[geneva] Add support for sending metrics in OTLP format over UDS

[CodeBlanch]

Changes

• Adds support for sending metrics in OTLP format over Unix domain sockets.

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 80.00000% with 8 lines in your changes missing coverage. Please review.

Project coverage is 56.85%. Comparing base (71655ce) to head (311c412).
Report is 566 commits behind head on main.

Files with missing lines	Patch %	Lines
...ry.Exporter.Geneva/Metrics/GenevaMetricExporter.cs	72.22%	5 Missing ⚠️
...s/Transport/MetricUnixDomainSocketDataTransport.cs	0.00%	2 Missing ⚠️
...Metrics/OtlpProtobuf/OtlpProtobufMetricExporter.cs	90.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #2261       +/-   ##
===========================================
- Coverage   73.91%   56.85%   -17.07%     
===========================================
  Files         267       45      -222     
  Lines        9615     4005     -5610     
===========================================
- Hits         7107     2277     -4830     
+ Misses       2508     1728      -780     

Flag	Coverage Δ
unittests-Exporter.Geneva	56.85% <80.00%> (?)

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

Files with missing lines	Coverage Δ
...eva/Metrics/OtlpProtobuf/OtlpProtobufSerializer.cs	90.00% <100.00%> (ø)
...Metrics/OtlpProtobuf/OtlpProtobufMetricExporter.cs	82.60% <90.00%> (ø)
...s/Transport/MetricUnixDomainSocketDataTransport.cs	0.00% <0.00%> (ø)
...ry.Exporter.Geneva/Metrics/GenevaMetricExporter.cs	87.75% <72.22%> (+21.08%)	⬆️

... and 244 files with indirect coverage changes

[cijothomas]

Something to consider in future: open-telemetry/opentelemetry-rust-contrib#104 (comment)

With UnixSockets, we are doing one call per MetricPoint (same for etw/user-events too). This may need revisit, especially for sockets.

[rajkumar-rangaraj]

LGTM