simplify async trait impl

[gruebel]

Changes

• streamlining the native async trait implementation

Merge requirement checklist

• CONTRIBUTING guidelines followed
• Unit tests added/updated (if applicable)
• Appropriate CHANGELOG.md files updated for non-trivial, user-facing changes
• Changes in public API reviewed (if applicable)

[codecov]

Codecov Report

Attention: Patch coverage is 55.55556% with 4 lines in your changes missing coverage. Please review.

Project coverage is 79.3%. Comparing base (37efb88) to head (328e847).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
opentelemetry-sdk/src/logs/log_processor.rs	0.0%	2 Missing ⚠️
...y-sdk/src/logs/log_processor_with_async_runtime.rs	0.0%	2 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #2692   +/-   ##
=====================================
  Coverage   79.2%   79.3%           
=====================================
  Files        123     123           
  Lines      22612   22602   -10     
=====================================
- Hits       17931   17927    -4     
+ Misses      4681    4675    -6     

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[lalitb]

Thanks.