Breaking: Move FlagCount and Flaggable to a public flag package

[FollowTheProcess]

Summary

First step in a re-think of how arguments and flags work, I want to make arguments similar to flags in that you define a structure and the args are parsed into type safe representations.

Adds a new public flag package for users to consume

• cli.FlagCount -> flag.Count
• cli.NoShortHand -> flag.NoShortHand

[codecov]

Codecov Report

❌ Patch coverage is 93.54839% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.50%. Comparing base (0b31428) to head (d626533).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/flag/flag.go	92.30%	1 Missing ⚠️
internal/flag/set.go	93.33%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #177   +/-   ##
=======================================
  Coverage   91.50%   91.50%           
=======================================
  Files           5        5           
  Lines        1260     1260           
=======================================
  Hits         1153     1153           
  Misses         61       61           
  Partials       46       46           

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