gh-134200: Add adaptive global alignment for help text

[lnperry]

Refactors HelpFormatter to improve help text readability and consistency,
addressing issues where argument string lengths varied widely.

Previously, a single very long option could push all help text excessively
to the right, or groups of only short options might not align optimally.

Key changes:

1. A global help alignment column is now calculated by finding the display
   endpoint of the longest "reasonable" argument invocation string across
   all sections, adding a 2-space padding.

   • A "reasonable" argument is one whose own invocation string (plus
     indent and minimal padding) does not exceed the overall maximum help
     position (derived from max_help_position and terminal width, e.g., 24).
   • This calculated alignment column is itself capped by this overall
     maximum help position.

2. Help text for arguments is formatted against this single global column:

   • Shorter arguments are padded so their help text (and any wrapped lines)
     begins at this alignment column.
   • Argument invocations too long to fit this same-line alignment will
     have their help text start on the next line, also indented to this
     alignment column.

This ensures:

• Consistent alignment of help descriptions across all sections.
• Outlier long options no longer distort the layout for other arguments.
• Sets of only short options are aligned compactly based on their local
  longest member, rather than being forced to an unnecessarily wide default.
• The option defining the alignment has exactly two spaces before its help.

• Issue: argparse argument help indent should discount very long argument names #134200

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[savannahostrowski]

Apologies for missing this back in May. Thanks for looking into this - I tested the changes and while they work as described, I think that the visual impact here is very minimal compared to code complexity this introduces. I'm also a bit concerned about the impact this will have on anyone whose tests depend on the current indentation. I don't think we should move forward with this change.

[savannahostrowski]

I've closed the corresponding issue for this so will also close this. Thanks again.