chore: add and harden Apache release tooling

[zjw1111]

Purpose

Linked issue: N/A

Prepare Apache Paimon C++ for its first Apache source release:

• apply the cmake-format result required by the post-merge pre-commit workflow
• replace GNU sed-only version parsing with portable POSIX awk parsing
• add version metadata validation and deterministic source archive auditing
• verify checksums, signatures, licenses, archive safety, build, tests, installation, and external CMake consumption
• add guarded RC staging and approved-release publishing scripts
• add a release-candidate workflow covering archive auditing, GCC 14, and Clang
• document ASF signing, voting, publication, and Paimon announcement requirements

The release orchestration validates that the candidate commit is contained in
the Apache release branch, waits for tag-triggered CI before uploading to
dist/dev, prevents --prepare-only runs from printing a vote email, and
supports resumable publication without overwriting release artifacts.

Tests

• pre-commit run --all-files
• bash -n scripts/releasing/*.sh ci/scripts/build_paimon.sh
• python3 -m unittest discover -s scripts/releasing/tests -v
• git diff --check
• created and audited the 0.2.3 source archive
• completed release build and all 25 tests from the extracted archive
• installed the release and built and ran an external CMake consumer

API and Format

No API, storage format, or protocol changes.

Documentation

Expanded scripts/releasing/README.md with the complete Apache release
preparation, verification, voting, publication, and announcement workflow.

Generative AI tooling

Generated-by: Codex (GPT-5)

[lxy-9602]

+1