Add Include what you use

[esigo]

related to #2054 (issue)

Changes

Adds Include what you use to the CI jobs that use clang.
The CI will not fail, only warning messages will be added e.g. here.

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

Merging #2214 (40de7b7) into main (31f218c) will not change coverage.
The diff coverage is n/a.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2214   +/-   ##
=======================================
  Coverage   87.51%   87.51%           
=======================================
  Files         169      169           
  Lines        4889     4889           
=======================================
  Hits         4278     4278           
  Misses        611      611           

see 2 files with indirect coverage changes

[marcalff]

LGTM as is.

This allows to see IWYU reports in the build logs, so we can start to take action and do some cleanup, even when reading logs to find issues is tedious (download the build log, search it).

Possible improvements, the CI most likely will need:

• a way to filter out IWYU complaints on code we do not own (third party headers, generated protobuf code)
• a way to summarize which file is / is not compliant, so that reading or searching logs is easier

This can be done later, once the code is cleaned up, so we can enforce a pass/fail result in CI.

Not sure if/how the github CI can report a warning, so it gets visibility in the overall build, and yet allow the build to pass.

[owent]

LGTM