[CI] speed up clang-tidy workflow

[sjinks]

Changes

This PR speeds up the clang-tidy workflow. Because clang-tidy only needs a compilation database generated by CMake, there's no need to waste time compiling the source code.

The only target we need to build is opentelemetry_proto because some other files depend on the files generated by the Protobuf compiler.

We can achieve further performance improvements by running clang-tidy jobs in parallel.

Before: 43:06 (number of warnings: 114)
After: 14:30 (number of warnings: 114)

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

[netlify]

✅ Deploy Preview for opentelemetry-cpp-api-docs canceled.

Name	Link
🔨 Latest commit	3ca6218
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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.82%. Comparing base (497eaf4) to head (3ca6218).
Report is 165 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3148      +/-   ##
==========================================
+ Coverage   87.12%   87.82%   +0.70%     
==========================================
  Files         200      195       -5     
  Lines        6109     6146      +37     
==========================================
+ Hits         5322     5397      +75     
+ Misses        787      749      -38     

see 113 files with indirect coverage changes

[marcalff]

LGTM, thanks for the CI speedup improvement.

[marcalff]

@sjinks Thanks for the fix, it is most welcome.

We are falling behind with basic checks like include-what-you-use (almost done) and clang-tidy (preliminary CI was set in place, but cleanup has barely started yet).

Contributions like yours, from someone having both the skills and the willingness to help, are definitively appreciated.