Experimental support for sub-classing ArgumentParser to customize add_argument

[mauvilsa]

What does this PR do?

Fixes #301 - change signature underscores to dashes
Fixes #355 - customize signature bool parameters

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• Did you update the documentation? (readme and public docstrings)
• Did you write unit tests such that there is 100% coverage on related code? (required for bug fixes and new features)
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• Did you make sure that all changes preserve backward compatibility?
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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (2285c1a) to head (e99fa1f).
Report is 1 commits behind head on main.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #661   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files           22        22           
  Lines         6631      6631           
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  Hits          6631      6631           

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[petergaultney]

i did some fairly rudimentary testing of my own and this seems to work. I appreciate you solving for the more general case that includes argument groups.