feat: use thread pool

[oraluben]

Use multithread to run IO-bounded jobs (e.g. shell command) concurrently.

Part of #545

TODO:

• cli argument
• doc
• test
• test time

[codecov]

Codecov Report

Attention: Patch coverage is 80.00000% with 10 lines in your changes missing coverage. Please review.

Project coverage is 91.65%. Comparing base (b01e842) to head (0cfd268).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
src/auditwheel/pool.py	67.85%	5 Missing and 4 partials ⚠️
src/auditwheel/repair.py	85.71%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #554      +/-   ##
==========================================
- Coverage   92.07%   91.65%   -0.43%     
==========================================
  Files          22       23       +1     
  Lines        1553     1593      +40     
  Branches      285      292       +7     
==========================================
+ Hits         1430     1460      +30     
- Misses         74       79       +5     
- Partials       49       54       +5     

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