Limiter extension interface: new admission limiter skeleton draft

[jmacd]

Description

This creates a skeleton for the proposed admission limiter based on the OTel-Arrow receiver's semaphore implementation, documented in https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/receiver/otelarrowreceiver/README.md#admission-control-configuration..

Link to tracking issue

Part of #9591.

Testing

Added. This is only a skeleton.

Documentation

TODO.

[codecov]

Codecov Report

Attention: Patch coverage is 90.90909% with 3 lines in your changes missing coverage. Please review.

Project coverage is 92.16%. Comparing base (79a0331) to head (828cf71).
Report is 11 commits behind head on main.

Files with missing lines	Patch %	Lines
...sion/admissionlimiterextension/admissionlimiter.go	81.81%	2 Missing ⚠️
extension/admissionlimiterextension/config.go	80.00%	1 Missing ⚠️

❌ Your patch status has failed because the patch coverage (90.90%) is below the target coverage (95.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #12602      +/-   ##
==========================================
- Coverage   92.18%   92.16%   -0.03%     
==========================================
  Files         469      475       +6     
  Lines       25394    25594     +200     
==========================================
+ Hits        23409    23588     +179     
- Misses       1574     1594      +20     
- Partials      411      412       +1     

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[jmacd]

See #12603 (comment).