Removed Moq dependency from Instrumentation.Grpc.Tests

[ngruson]

Related to #4758.

Changes

• Refactored GrpcTests.client
• Removed Moq dependency

[codecov]

Codecov Report

Merging #5124 (8a2f9c4) into main (f11801d) will decrease coverage by 0.01%.
Report is 1 commits behind head on main.
The diff coverage is n/a.

❗ Current head 8a2f9c4 differs from pull request most recent head eddaca3. Consider uploading reports for the commit eddaca3 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5124      +/-   ##
==========================================
- Coverage   83.07%   83.06%   -0.01%     
==========================================
  Files         296      296              
  Lines       12320    12320              
==========================================
- Hits        10235    10234       -1     
- Misses       2085     2086       +1     

Flag	Coverage Δ
unittests	83.06% <ø> (-0.01%)	⬇️

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see 6 files with indirect coverage changes