Add new parse and format packages to reduce duplication

[FollowTheProcess]

• Add an internal parse package for type safe parsing
• Add cast to the parse package
• Add a format package to do the inverse
• Add type names to the format package

Summary

[codecov]

Codecov Report

❌ Patch coverage is 82.63473% with 29 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.32%. Comparing base (6769943) to head (bed0cf9).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/parse/parse.go	75.00%	16 Missing ⚠️
internal/arg/arg.go	86.31%	13 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #179      +/-   ##
==========================================
- Coverage   87.06%   86.32%   -0.75%     
==========================================
  Files           5        7       +2     
  Lines        1477     1514      +37     
==========================================
+ Hits         1286     1307      +21     
- Misses        129      145      +16     
  Partials       62       62              

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