[Exporter.Geneva] Add TraceState support

[xiang17]

Add TraceState support in Geneva exporter.

Changes

Please provide a brief description of the changes here.

For significant contributions please make sure you have completed the following items:

• Appropriate CHANGELOG.md updated for non-trivial changes
• Design discussion issue #
• Changes in public API reviewed

[codecov]

Codecov Report

Attention: Patch coverage is 64.28571% with 5 lines in your changes missing coverage. Please review.

Project coverage is 65.57%. Comparing base (71655ce) to head (123f26e).
Report is 304 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1850      +/-   ##
==========================================
- Coverage   73.91%   65.57%   -8.35%     
==========================================
  Files         267       35     -232     
  Lines        9615     3660    -5955     
==========================================
- Hits         7107     2400    -4707     
+ Misses       2508     1260    -1248     

Flag	Coverage Δ
unittests-Exporter.Geneva	65.57% <64.28%> (?)

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

Files	Coverage Δ
...Telemetry.Exporter.Geneva/GenevaExporterOptions.cs	90.24% <100.00%> (+0.24%)	⬆️
...ter.Geneva/MsgPackExporter/MsgPackTraceExporter.cs	94.83% <100.00%> (+2.41%)	⬆️
...ry.Exporter.Geneva/TLDExporter/TldTraceExporter.cs	32.75% <16.66%> (+0.44%)	⬆️

... and 248 files with indirect coverage changes

[rajkumar-rangaraj]

LGTM

[reyang]

LGTM.