Fix test for Windows upgrade check.

[fnando]

No description provided.

[Copilot]

Pull request overview

This PR aims to stabilize the Windows upgrade-check related tests by preventing cross-test interference from shared environment variables during parallel test execution.

Changes:

• Mark affected unit tests as serial to avoid parallel env var mutation.
• Update the upgrade check test to prefer STELLAR_DATA_HOME (higher priority and cross-platform) and to clear XDG_DATA_HOME.
• Add serial_test as a dev-dependency (and update Cargo.lock accordingly).

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 1 comment.

File	Description
cmd/soroban-cli/src/config/upgrade_check.rs	Makes the upgrade check load/save test run serially and uses STELLAR_DATA_HOME for deterministic temp dir resolution.
cmd/soroban-cli/src/config/data.rs	Makes the write/read cache test run serially to reduce env var test interference.
cmd/soroban-cli/Cargo.toml	Adds serial_test under dev-dependencies to support serial test execution.
Cargo.lock	Locks the new serial_test dependency.

Comments suppressed due to low confidence (1)

cmd/soroban-cli/src/config/data.rs:212

• STELLAR_DATA_HOME is set for the test but never restored/removed afterward, which can leak into other tests and cause order-dependent failures. Save the original value at the start of the test and restore it at the end (or remove it if it was unset). Also, set_var can take an OsStr, so you can avoid to_str().unwrap() by passing the Path directly to prevent a potential panic on non-UTF8 paths.

    fn test_write_read() {
        let t = assert_fs::TempDir::new().unwrap();
        std::env::set_var("STELLAR_DATA_HOME", t.path().to_str().unwrap());
        let rpc_uri = Url::from_str("http://localhost:8000").unwrap();