feat(pool): add option to bound task queue

[alitto]

• Add support to create bounded pools by specifying a queue size (WithQueueSize option).
• Add support to choose how to deal with tasks submitted when the queue is full (WithNonBlocking option).
• Create custom implementation of a semaphore and refactor subpools to use it.
• Bump minimum supported go version to 1.21 since the semaphore package requires context.AfterFunc.
• Ensure RunningWorkers() method in subpools reflect the actual number of workers running tasks belonging to the subpool.
• Allow overriding pool options when creating a subpool via NewSupool.

[codecov]

Codecov Report

Attention: Patch coverage is 87.72727% with 27 lines in your changes missing coverage. Please review.

Project coverage is 93.87%. Comparing base (ac7c6a3) to head (20335af).

Files with missing lines	Patch %	Lines
resultsubpool.go	46.15%	16 Missing and 5 partials ⚠️
pool.go	84.61%	3 Missing and 1 partial ⚠️
internal/linkedbuffer/linkedbuffer.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #95      +/-   ##
==========================================
- Coverage   95.32%   93.87%   -1.46%     
==========================================
  Files          14       15       +1     
  Lines         855     1028     +173     
==========================================
+ Hits          815      965     +150     
- Misses         36       52      +16     
- Partials        4       11       +7     

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