docs(release): update changelog for the 2026-05 release

[scotthart]

No description provided.

[gemini-code-assist]

Code Review

This pull request prepares the v3.5.0 release by removing the release candidate suffix from CMake, Bazel, and internal version headers. It also updates the CHANGELOG.md with release notes for Bigtable and Storage components. Review feedback suggests standardizing the changelog descriptions by using lowercase for the first word of each entry to maintain consistency with conventional commit formatting.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.68%. Comparing base (75ce2e8) to head (5cee68a).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #16097      +/-   ##
==========================================
- Coverage   92.69%   92.68%   -0.01%     
==========================================
  Files        2353     2353              
  Lines      218328   218328              
==========================================
- Hits       202373   202363      -10     
- Misses      15955    15965      +10     

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