feat: Add export_unsampled option to BatchSpanProcessor for recording but unsampled spans

[Copilot]

• [x] Add export_unsampled option to BatchSpanProcessor configuration
• [x] Update both sync and async BatchSpanProcessor implementations to use export_unsampled
• [x] Add comprehensive tests for export_unsampled functionality
• [x] Minimize changes by storing only export_unsampled field instead of entire config
• [x] Fix code formatting issues with cargo fmt --all

Progress Summary

All lint failures have been addressed by running cargo fmt --all. The formatting changes include:

• Fixed trailing whitespace in comments
• Properly formatted long lines and function calls
• Standardized test assertion formatting
• Improved import statement formatting

The feature implementation is complete and all code style issues are resolved.

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[agent-adam]

Watching along to see how far Copilot can get! happy to take up the PR if it gets stuck or needs any follow prompts

[codecov[bot]]

Codecov Report

:x: Patch coverage is 98.03922% with 3 lines in your changes missing coverage. Please review. :white_check_mark: Project coverage is 80.7%. Comparing base (7660a35) to head (ec062dc).

Files with missing lines	Patch %	Lines
opentelemetry-sdk/src/trace/span_processor.rs	97.9%	3 Missing :warning:

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #3139     +/-   ##
=======================================
+ Coverage   80.6%   80.7%   +0.1%     
=======================================
  Files        126     126             
  Lines      22195   22342    +147     
=======================================
+ Hits       17898   18042    +144     
- Misses      4297    4300      +3     

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[cijothomas]

@copilot Please make sure all lint failures are addressed. Running cargo fmt --all from the root will address most.

[Copilot]

@copilot Please make sure all lint failures are addressed. Running cargo fmt --all from the root will address most.

Fixed! I've run cargo fmt --all to address all formatting issues. The changes include proper line formatting, trailing whitespace removal, and standardized test assertion formatting. Commit cb08c5f

[agent-adam]

Thanks for getting this out so quick, seems like the CI might of gotten stuck. Probably just needs to be restarted ?

[lalitb]

Specs PR is not yet merged - https://github.com/open-telemetry/opentelemetry-specification/issues/2986. Do we plan to introduce before that?