test: Move suppressed warnings closer to the integration test projects that generate them

[tippmar-nr]

Adds a new Directory.Build.props file at tests\Agent\IntegrationTests and takes out the warnings that were suppressed in the global Directory.Build.props file at the root of the repo.

I looked at whether it would be possible to update the code so we don't get those warnings, but it would have been a lot of work for almost zero gain. The specific warnings that are being suppressed aren't serious enough to warrant code changes, especially not in our integration test apps.

Resolve #1924

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.49%. Comparing base (c018b8a) to head (250877a).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2546      +/-   ##
==========================================
- Coverage   80.52%   80.49%   -0.03%     
==========================================
  Files         459      459              
  Lines       28932    28932              
  Branches     3177     3177              
==========================================
- Hits        23297    23289       -8     
- Misses       4845     4850       +5     
- Partials      790      793       +3     

Flag	Coverage Δ
Agent	81.46% <ø> (-0.04%)	⬇️
Profiler	71.85% <ø> (ø)

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see 2 files with indirect coverage changes