[CI] upgrade to clang-tidy 20

[dbarker]

Fixes #3538

To run clang-tidy on all header files we need to upgrade to version 20.1. This version adds the --exclude-header-filter argument enabling analysis of all project header files excluding the api/.../internal/absl headers.

Changes

• upgrade the clang-tidy CI workflow and devcontainer to clang-tidy version 20 from version 18
• adds a python script to parse the build logs and create a markdown report on the unique warnings found

For significant contributions please make sure you have completed the following items:

• CHANGELOG.md updated for non-trivial changes
• Unit tests have been added
• Changes in public API reviewed

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.95%. Comparing base (bed305f) to head (be9b574).
⚠️ Report is 23 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3762      +/-   ##
==========================================
+ Coverage   89.95%   89.95%   +0.01%     
==========================================
  Files         225      225              
  Lines        7158     7163       +5     
==========================================
+ Hits         6438     6443       +5     
  Misses        720      720              

see 5 files with indirect coverage changes

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[marcalff]

@dbarker

The generated reports (seen in CI) are very nice.

[marcalff]

LGTM, great work.