implement resource attributes for geneva logs

[mattsains]

Changes

This follows up on #3214 by implementing similar behaviour for including resource attributes in Geneva Logs.

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

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 68.61%. Comparing base (6a43b08) to head (2f4d319).
⚠️ Report is 7 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3531      +/-   ##
==========================================
- Coverage   70.92%   68.61%   -2.32%     
==========================================
  Files         430      429       -1     
  Lines       17214    17134      -80     
==========================================
- Hits        12209    11756     -453     
- Misses       5005     5378     +373     

Flag	Coverage Δ
unittests-Exporter.Geneva	45.59% <100.00%> (-8.06%)	⬇️

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

Files with missing lines	Coverage Δ
...Telemetry.Exporter.Geneva/GenevaExporterOptions.cs	90.24% <ø> (ø)
...OpenTelemetry.Exporter.Geneva/GenevaLogExporter.cs	62.50% <100.00%> (-25.00%)	⬇️
...rter.Geneva/Internal/MsgPack/MsgPackLogExporter.cs	91.66% <100.00%> (-0.65%)	⬇️

... and 20 files with indirect coverage changes

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