ci: separate out storage emulator from cxx20 builds

[scotthart]

No description provided.

[gemini-code-assist]

Code Review

This pull request refactors the C++20 CI/CD integration test pipeline to run Google Cloud Storage integration tests separately from other integration tests. It introduces new Cloud Build triggers and modifies the build scripts to conditionally execute tests based on the INTEGRATION_LIBRARIES environment variable. The review feedback suggests scoping variables locally within the newly added integration::ctest_storage_with_emulators function by using local -r for EMULATOR_SCRIPT and declaring ctest_args as a local array to prevent global namespace pollution.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.19%. Comparing base (4112803) to head (4a953e8).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #16167      +/-   ##
==========================================
- Coverage   92.21%   92.19%   -0.02%     
==========================================
  Files        2264     2265       +1     
  Lines      209092   209121      +29     
==========================================
- Hits       192811   192809       -2     
- Misses      16281    16312      +31     

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