Fix: Prevent broken traces when HttpClient content headers contain tracing headers. (#1843)

[nrcventura]

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Description

Fixes #1843.

Prevents duplicate outgoing tracing headers, for HttpClient calls, by ensuring that the headers are only present as request headers, and that they do not also appear as content headers. An existing Integration Test was updated to ensure that the distributed trace is not broken when tracing headers are part of the Content Headers collection.

Author Checklist

• Unit tests, Integration tests, and Unbounded tests completed
• Performance testing completed with satisfactory results (if required)

Reviewer Checklist

• Perform code review
• Pull request was adequately tested (new/existing tests, performance tests)

[codecov-commenter]

Codecov Report

Merging #1888 (a940b3e) into main (737b4f1) will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1888      +/-   ##
==========================================
- Coverage   83.49%   83.48%   -0.01%     
==========================================
  Files         402      402              
  Lines       24670    24670              
==========================================
- Hits        20597    20596       -1     
- Misses       4073     4074       +1     

see 1 file with indirect coverage changes

[tippmar-nr]

Nicely done!