Mobile,Desktop: Fixes #11135: Fix incorrect list switching behavior

[personalizedrefrigerator]

Summary

This pull request fixes incorrect regular expressions for numbered lists and checklists.

Previously, the numbered and checklist regular expressions did not require a space after the first number (so "1.a" would be considered a list item).

Fixes #11135.

Screen recording

Screencast.from.2024-09-27.12-23-17.webm

Possible future improvements

1. Use CodeMirror's syntax tree to determine whether a list type is already selected, rather than using a custom regular expression.
   • This may lead to more fragile tests — in the past there have been random CI failures due to the CodeMirror syntax tree not being present.
2. Don't try to remove a list if: 1) the user has selected text and 2) the text seems to be only part of a larger list.

Testing plan

This pull request includes an automated test.

[laurent22]

That looks good, thank you for fixing this!