[OTLP] Fix OTLP/gRPC status parsing

[Kielek]

Fixes issues dected by Codex/security scans

Changes

Fixed an issue in OTLP/gRPC retry handling where parsing gRPC status for some malformed data.

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

❌ Patch coverage is 90.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 88.36%. Comparing base (feb588b) to head (6633db8).
⚠️ Report is 5 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...tation/ExportClient/Grpc/GrpcStatusDeserializer.cs	90.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7064      +/-   ##
==========================================
- Coverage   88.39%   88.36%   -0.04%     
==========================================
  Files         270      270              
  Lines       12758    12768      +10     
==========================================
+ Hits        11278    11282       +4     
- Misses       1480     1486       +6     

Flag	Coverage Δ
unittests-Project-Experimental	88.01% <90.00%> (-0.34%)	⬇️
unittests-Project-Stable	88.16% <90.00%> (-0.08%)	⬇️

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

Files with missing lines	Coverage Δ
...tation/ExportClient/Grpc/GrpcStatusDeserializer.cs	87.59% <90.00%> (+0.18%)	⬆️

... and 2 files with indirect coverage changes

[martincostello]

Coincidentally I found this myself yesterday evening. Once I'm at my laptop I'll copy-paste the test I have locally that I hadn't pushed that's a bit more comprehensive.