chore: Make materializer stackless for obj and arr (#620)

Motivation:
This can reduce some stack usage of the jvm native frame

refs:google/jsonnet#1142

on main
```
125] Benchmark                                                                  (path)  Mode  Cnt   Score   Error  Units
125] RegressionBenchmark.main             bench/resources/bug_suite/assertions.jsonnet  avgt        0.271          ms/op
125] RegressionBenchmark.main               bench/resources/cpp_suite/bench.01.jsonnet  avgt        0.067          ms/op
125] RegressionBenchmark.main               bench/resources/cpp_suite/bench.02.jsonnet  avgt       42.941          ms/op
125] RegressionBenchmark.main               bench/resources/cpp_suite/bench.03.jsonnet  avgt       12.480          ms/op
125] RegressionBenchmark.main               bench/resources/cpp_suite/bench.04.jsonnet  avgt       31.739          ms/op
125] RegressionBenchmark.main               bench/resources/cpp_suite/bench.06.jsonnet  avgt        0.397          ms/op
125] RegressionBenchmark.main               bench/resources/cpp_suite/bench.07.jsonnet  avgt        3.589          ms/op
125] RegressionBenchmark.main               bench/resources/cpp_suite/bench.08.jsonnet  avgt        0.056          ms/op
125] RegressionBenchmark.main               bench/resources/cpp_suite/bench.09.jsonnet  avgt        0.063          ms/op
125] RegressionBenchmark.main         bench/resources/cpp_suite/gen_big_object.jsonnet  avgt        0.936          ms/op
125] RegressionBenchmark.main      bench/resources/cpp_suite/large_string_join.jsonnet  avgt        2.312          ms/op
125] RegressionBenchmark.main  bench/resources/cpp_suite/large_string_template.jsonnet  avgt        2.288          ms/op
125] RegressionBenchmark.main             bench/resources/cpp_suite/realistic1.jsonnet  avgt        2.965          ms/op
125] RegressionBenchmark.main             bench/resources/cpp_suite/realistic2.jsonnet  avgt       71.454          ms/op
125] RegressionBenchmark.main                  bench/resources/go_suite/base64.jsonnet  avgt        0.787          ms/op
125] RegressionBenchmark.main            bench/resources/go_suite/base64Decode.jsonnet  avgt        0.595          ms/op
125] RegressionBenchmark.main       bench/resources/go_suite/base64DecodeBytes.jsonnet  avgt        9.178          ms/op
125] RegressionBenchmark.main       bench/resources/go_suite/base64_byte_array.jsonnet  avgt        1.416          ms/op
125] RegressionBenchmark.main              bench/resources/go_suite/comparison.jsonnet  avgt       23.242          ms/op
125] RegressionBenchmark.main             bench/resources/go_suite/comparison2.jsonnet  avgt       72.070          ms/op
125] RegressionBenchmark.main        bench/resources/go_suite/escapeStringJson.jsonnet  avgt        0.048          ms/op
125] RegressionBenchmark.main                   bench/resources/go_suite/foldl.jsonnet  avgt        9.089          ms/op
125] RegressionBenchmark.main             bench/resources/go_suite/lstripChars.jsonnet  avgt        0.609          ms/op
125] RegressionBenchmark.main          bench/resources/go_suite/manifestJsonEx.jsonnet  avgt        0.069          ms/op
125] RegressionBenchmark.main          bench/resources/go_suite/manifestTomlEx.jsonnet  avgt        0.085          ms/op
125] RegressionBenchmark.main         bench/resources/go_suite/manifestYamlDoc.jsonnet  avgt        0.072          ms/op
125] RegressionBenchmark.main                  bench/resources/go_suite/member.jsonnet  avgt        0.707          ms/op
125] RegressionBenchmark.main                bench/resources/go_suite/parseInt.jsonnet  avgt        0.050          ms/op
125] RegressionBenchmark.main                 bench/resources/go_suite/reverse.jsonnet  avgt       11.035          ms/op
125] RegressionBenchmark.main             bench/resources/go_suite/rstripChars.jsonnet  avgt        0.590          ms/op
125] RegressionBenchmark.main              bench/resources/go_suite/stripChars.jsonnet  avgt        0.584          ms/op
125] RegressionBenchmark.main                  bench/resources/go_suite/substr.jsonnet  avgt        0.159          ms/op
125] RegressionBenchmark.main           bench/resources/sjsonnet_suite/setDiff.jsonnet  avgt        0.485          ms/op
125] RegressionBenchmark.main          bench/resources/sjsonnet_suite/setInter.jsonnet  avgt        0.435          ms/op
125] RegressionBenchmark.main          bench/resources/sjsonnet_suite/setUnion.jsonnet  avgt        0.723          ms/op
125/125, SUCCESS] ./mill bench.runRegressions 434s

```


with this

```
125] Benchmark                                                                  (path)  Mode  Cnt   Score   Error  Units
125] RegressionBenchmark.main             bench/resources/bug_suite/assertions.jsonnet  avgt        0.297          ms/op
125] RegressionBenchmark.main               bench/resources/cpp_suite/bench.01.jsonnet  avgt        0.068          ms/op
125] RegressionBenchmark.main               bench/resources/cpp_suite/bench.02.jsonnet  avgt       39.359          ms/op
125] RegressionBenchmark.main               bench/resources/cpp_suite/bench.03.jsonnet  avgt       12.130          ms/op
125] RegressionBenchmark.main               bench/resources/cpp_suite/bench.04.jsonnet  avgt       30.164          ms/op
125] RegressionBenchmark.main               bench/resources/cpp_suite/bench.06.jsonnet  avgt        0.418          ms/op
125] RegressionBenchmark.main               bench/resources/cpp_suite/bench.07.jsonnet  avgt        3.256          ms/op
125] RegressionBenchmark.main               bench/resources/cpp_suite/bench.08.jsonnet  avgt        0.057          ms/op
125] RegressionBenchmark.main               bench/resources/cpp_suite/bench.09.jsonnet  avgt        0.064          ms/op
125] RegressionBenchmark.main         bench/resources/cpp_suite/gen_big_object.jsonnet  avgt        0.982          ms/op
125] RegressionBenchmark.main      bench/resources/cpp_suite/large_string_join.jsonnet  avgt        2.111          ms/op
125] RegressionBenchmark.main  bench/resources/cpp_suite/large_string_template.jsonnet  avgt        2.250          ms/op
125] RegressionBenchmark.main             bench/resources/cpp_suite/realistic1.jsonnet  avgt        2.945          ms/op
125] RegressionBenchmark.main             bench/resources/cpp_suite/realistic2.jsonnet  avgt       65.150          ms/op
125] RegressionBenchmark.main                  bench/resources/go_suite/base64.jsonnet  avgt        0.815          ms/op
125] RegressionBenchmark.main            bench/resources/go_suite/base64Decode.jsonnet  avgt        0.626          ms/op
125] RegressionBenchmark.main       bench/resources/go_suite/base64DecodeBytes.jsonnet  avgt        9.380          ms/op
125] RegressionBenchmark.main       bench/resources/go_suite/base64_byte_array.jsonnet  avgt        1.443          ms/op
125] RegressionBenchmark.main              bench/resources/go_suite/comparison.jsonnet  avgt       22.236          ms/op
125] RegressionBenchmark.main             bench/resources/go_suite/comparison2.jsonnet  avgt       76.674          ms/op
125] RegressionBenchmark.main        bench/resources/go_suite/escapeStringJson.jsonnet  avgt        0.049          ms/op
125] RegressionBenchmark.main                   bench/resources/go_suite/foldl.jsonnet  avgt        9.004          ms/op
125] RegressionBenchmark.main             bench/resources/go_suite/lstripChars.jsonnet  avgt        0.643          ms/op
125] RegressionBenchmark.main          bench/resources/go_suite/manifestJsonEx.jsonnet  avgt        0.069          ms/op
125] RegressionBenchmark.main          bench/resources/go_suite/manifestTomlEx.jsonnet  avgt        0.084          ms/op
125] RegressionBenchmark.main         bench/resources/go_suite/manifestYamlDoc.jsonnet  avgt        0.073          ms/op
125] RegressionBenchmark.main                  bench/resources/go_suite/member.jsonnet  avgt        0.708          ms/op
125] RegressionBenchmark.main                bench/resources/go_suite/parseInt.jsonnet  avgt        0.051          ms/op
125] RegressionBenchmark.main                 bench/resources/go_suite/reverse.jsonnet  avgt       11.257          ms/op
125] RegressionBenchmark.main             bench/resources/go_suite/rstripChars.jsonnet  avgt        0.641          ms/op
125] RegressionBenchmark.main              bench/resources/go_suite/stripChars.jsonnet  avgt        0.624          ms/op
125] RegressionBenchmark.main                  bench/resources/go_suite/substr.jsonnet  avgt        0.159          ms/op
125] RegressionBenchmark.main           bench/resources/sjsonnet_suite/setDiff.jsonnet  avgt        0.488          ms/op
125] RegressionBenchmark.main          bench/resources/sjsonnet_suite/setInter.jsonnet  avgt        0.423          ms/op
125] RegressionBenchmark.main          bench/resources/sjsonnet_suite/setUnion.jsonnet  avgt        0.743          ms/op
125/125, SUCCESS] ./mill bench.runRegressions 434s

```

Author: He-Pin

readme.md

@@ -292,6 +292,25 @@ To generate the static files without starting a server:
 
 The output is a single `index.html` file (with the Sjsonnet JS engine inlined) written to `out/playground/bundle.dest/`. You can open it directly in a browser — no server needed — or serve it with any static file server. The editor UI (CodeMirror) is loaded from a CDN at runtime, so an internet connection is required.
 
+## Development
+To compile the JVM version:
+
+```bash
+./mill 'sjsonnet.jvm[3.3.7]'.compile
+```
+
+To run the tests:
+
+```bash
+./mill 'sjsonnet.jvm[3.3.7]'.test
+```
+
+If you want to test for all platforms and versions, you can run
+
+```bash
+./mill __.test
+```
+
 ## Client-Server
 
 Sjsonnet comes with a built in thin-client and background server, to help