Improve error message for deprecated hash-to-curve strategy

[changtong9]

No description provided.

[gemini-code-assist]

Summary of Changes

Hello @changtong9, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request focuses on refining the cryptographic module by improving the clarity and helpfulness of error messages related to deprecated hash-to-curve strategies. It guides developers towards more secure and interoperable alternatives while simultaneously cleaning up the associated test infrastructure to reflect these updated best practices. The changes ensure that users receive actionable advice when encountering deprecated functionality and that the codebase remains lean and relevant.

Highlights

• Improved Error Message: The error message for the deprecated HashToCurveStrategy::TryAndRehash_SHA2 has been significantly enhanced to provide clearer guidance. It now recommends using curve-specific, standard-compliant strategies for better security and interoperability, with examples for NIST curves (e.g., SHA256_SSWU_RO_) and the SM2 curve (e.g., TryAndRehash_SM).
• Test Code Cleanup: Obsolete and commented-out test cases related to deprecated hash-to-curve strategies (like TryAndRehash_SHA2 and TryAndRehash_BLAKE3) have been removed from openssl_test.cc, streamlining the test suite and focusing on currently supported methods.

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[gemini-code-assist]

Code Review

This pull request improves the error message for the deprecated HashToCurveStrategy::TryAndRehash_SHA2. The new message is more informative, explaining why the strategy is deprecated and suggesting secure alternatives. The change also includes removing commented-out test code related to this deprecated strategy. Overall, this is a good enhancement for developer experience and code maintainability.

[Jamie-Cui]

LGTM