Add release automation and documentation

[sduvvuri1603]

Description of your changes:

• .github/workflows/build-packages.yml: converted into a reusable workflow that still performs the matrix build/validation but now also handles release-mode tasks—regenerating artifacts from the sdist, running twine check, and optionally publishing to PyPI via the Trusted Publishing path. That’s the core enhancement.
• Introduced .github/workflows/release.yml, which triggers on vX.Y.Z tags and reuses the build workflow in publish mode (single Python 3.11 job with secrets: inherit).
• Authored docs/RELEASE.md covering versioning requirements, step-by-step release procedure, workflow behavior, and PyPI rollback guidance.

[google-oss-prow]

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[VaniHaripriya]

Could you add a step to upload the packages as release artifacts.

[VaniHaripriya]

I think we should add automatic changelog generation using git-cliff. @mprahl @HumairAK could you share your thoughts on this?