[Logs Bridge API] Add support for Body set directly on LogRecord for OTLP Exporter.

[Yun-Ting]

Changes

Towards #4433
Added support for Body set directly on LogRecord via the Logs Bridge API.

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: 21 lines in your changes are missing coverage. Please review.

Comparison is base (6250307) 83.38% compared to head (f4de1f5) 83.12%.
Report is 48 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5268      +/-   ##
==========================================
- Coverage   83.38%   83.12%   -0.27%     
==========================================
  Files         297      272      -25     
  Lines       12531    11975     -556     
==========================================
- Hits        10449     9954     -495     
+ Misses       2082     2021      -61     

Flag	Coverage Δ
unittests	?
unittests-Solution-Experimental	83.02% <77.41%> (?)
unittests-Solution-Stable	83.09% <77.41%> (?)

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

Files	Coverage Δ
....Api/Context/Propagation/TraceContextPropagator.cs	90.00% <100.00%> (+0.52%)	⬆️
...etryProtocol/Implementation/ExperimentalOptions.cs	100.00% <ø> (ø)
...tation/OpenTelemetryProtocolExporterEventSource.cs	100.00% <100.00%> (ø)
...rotocol/Implementation/OtlpLogRecordTransformer.cs	95.41% <100.00%> (+1.95%)	⬆️
...tation.AspNetCore/Implementation/HttpInListener.cs	89.79% <100.00%> (+0.21%)	⬆️
...AspNetCore/Implementation/HttpInMetricsListener.cs	89.74% <100.00%> (+0.26%)	⬆️
...ntation.GrpcNetClient/GrpcClientInstrumentation.cs	100.00% <100.00%> (ø)
...NetClient/GrpcClientTraceInstrumentationOptions.cs	100.00% <ø> (ø)
...ent/Implementation/GrpcClientDiagnosticListener.cs	75.80% <100.00%> (-2.77%)	⬇️
...n.GrpcNetClient/TracerProviderBuilderExtensions.cs	100.00% <100.00%> (ø)
... and 13 more

... and 35 files with indirect coverage changes

[CodeBlanch]

LGTM

[vishweshbankwar]

LGTM: left couple nits.