[Exporter.Geneva] Add thread-safety regression tests for MsgPackTraceExporter and MsgPackLogExporter

[mattsains]

This PR is based on #3882

Changes

Added two tests that run the log and trace exporter in parallel looking for race conditions

Merge requirement checklist

• CONTRIBUTING guidelines followed (license requirements, nullable enabled, static analysis, etc.)
• Unit tests added/updated
• [n/a] Appropriate CHANGELOG.md files updated for non-trivial changes
• [n/a] Changes in public API reviewed (if applicable)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.03%. Comparing base (4a4fab7) to head (ce7ac07).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3886      +/-   ##
==========================================
+ Coverage   71.59%   72.03%   +0.43%     
==========================================
  Files         447      447              
  Lines       17827    17815      -12     
==========================================
+ Hits        12764    12833      +69     
+ Misses       5063     4982      -81     

Flag	Coverage Δ
unittests-Exporter.Geneva	54.60% <ø> (+0.03%)	⬆️

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see 13 files with indirect coverage changes

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[rajkumar-rangaraj]

LGTM