[otlp] OTLP Exporter Custom serializer - Complete Traces

[rajkumar-rangaraj]

Fixes Part of #5730, Follow up #5928
Design discussion issue #

Changes

Please provide a brief description of the changes here.

This change completes the implementation of the trace serialization.

Merge requirement checklist

• CONTRIBUTING guidelines followed (license requirements, nullable enabled, static analysis, etc.)
• Unit tests added/updated
• Appropriate CHANGELOG.md files updated for non-trivial changes
• Changes in public API reviewed (if applicable)

[codecov]

Codecov Report

Attention: Patch coverage is 91.53846% with 11 lines in your changes missing coverage. Please review.

Project coverage is 86.34%. Comparing base (6250307) to head (7523a86).
Report is 366 commits behind head on main.

Files with missing lines	Patch %	Lines
...entation/Serializer/ProtobufOtlpTraceSerializer.cs	89.42%	11 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5930      +/-   ##
==========================================
+ Coverage   83.38%   86.34%   +2.96%     
==========================================
  Files         297      261      -36     
  Lines       12531    11690     -841     
==========================================
- Hits        10449    10094     -355     
+ Misses       2082     1596     -486     

Flag	Coverage Δ
unittests	?
unittests-Project-Experimental	86.25% <91.53%> (?)
unittests-Project-Stable	86.07% <91.53%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...ation/Serializer/ProtobufOtlpResourceSerializer.cs	88.23% <100.00%> (ø)
...Implementation/Serializer/ProtobufOtlpTagWriter.cs	94.64% <100.00%> (ø)
...entation/Serializer/ProtobufOtlpTraceSerializer.cs	89.51% <89.42%> (ø)

... and 242 files with indirect coverage changes

[CodeBlanch]

LGTM