Add signTypedData address recovery test (#2019)

[Sukuna0007Abhi]

What does this PR do?

Adds a focused unit test to demonstrate and verify how to recover the signer address from a signTypedData signature.

Specifically:

1. Reuses the existing typed-data JSON fixture in SignTest.
2. Signs the typed data with Sign.signTypedData(...).
3. Recomputes the structured-data hash via StructuredDataEncoder.hashStructuredData().
4. Recovers the public key using Sign.signedMessageHashToKey(...).
5. Derives and asserts the recovered address matches SampleKeys.ADDRESS

Where should the reviewer start?

Start in crypto/src/test/java/org/web3j/crypto/SignTest.java, especially:

The new typed-data fixture constant near the top of the class.
testRecoverAddressFromSignTypedData() for the recovery flow.
testSignTypedData() which now reuses the shared fixture.

Why is it needed?

Issue #2019 identifies a real gap: while signTypedData signing is tested, recovery/verification flow is not clearly demonstrated in tests.

This PR closes that gap by adding an executable example that:

• Serves as documentation for users verifying typed-data signatures.
• Improves confidence in end-to-end signing + recovery behavior.
• Increases robustness of the crypto test suite without changing production behavior.

Checklist

• I've read the contribution guidelines.
• I've added tests (if applicable).
• I've added a changelog entry if necessary.