[OTLP] include status code in failure log

[TimothyMothra]

Fixes #
Design discussion issue #

Changes

The current log omits the Status Code, but that's needed to investigate any failures.

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)

[Kielek]

LGTM

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.34%. Comparing base (7521728) to head (661fa69).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6154      +/-   ##
==========================================
- Coverage   86.34%   86.34%   -0.01%     
==========================================
  Files         257      257              
  Lines       11559    11556       -3     
==========================================
- Hits         9981     9978       -3     
  Misses       1578     1578              

Files with missing lines	Coverage Δ
...mplementation/ExportClient/OtlpGrpcExportClient.cs	66.27% <ø> (-0.39%)	⬇️
...tation/OpenTelemetryProtocolExporterEventSource.cs	80.82% <100.00%> (-0.52%)	⬇️