sort `python --help-xoptions` & `--help-env` to make them easier to visually scan

[gpshead]

Documentation

Now that we've gained so many -X options over the years an unsorted mess actually looks like a mess. --help-env also in need of this. It's runtime but it is just help text, thus the docs label. I'll backport as reasonable. The PRs include test_cmd_line regression tests so we maintain the ordering going forward.

Linked PRs

• gh-145990: Sort python --help-xoptions by option name #145991
• [3.14] gh-145990: Sort python --help-xoptions by option name #145993
• gh-145990: sort --help-env sections by environment variable name #145997
• [3.14] gh-145990: sort --help-env sections by environment variable name #146001
• [3.13] gh-145990: sort --help-env first section by name (others and xoptions already sorted) #146003