Move exit dialog to submodule

[seanbudd]

Link to issue number:

None

Summary of the issue:

When working on #13488, the exitDialog was lengthened, and probably should be moved to its own submodule file.

Description of how this pull request fixes the issue:

Moves and lints ExitDialog and _ExitAction from gui.__init__ into gui.exit.

Testing strategy:

• Review the move commit with git show ea52996ae9a3ae7a2a536d5298bce9d8595e24be --color-moved
• Review linting manually git show ea2c04119
• Review the CRLF change with git show 196b55dc8 --ignore-cr-at-eol
• Run NVDA and opening the exit dialog
• Ensure Disable logging in secure mode #13488 isn't reintroduced

Known issues with pull request:

None

Change log entries:

For Developers

- ``gui.quit`` has been deprecated for removal in 2023.1. (#13498)

Code Review Checklist:

• Pull Request description:
  • description is up to date
  • change log entries
• Testing:
  • Unit tests
  • System (end to end) tests
  • Manual testing
• API is compatible with existing add-ons.
• Documentation:
  • User Documentation
  • Developer / Technical Documentation
  • Context sensitive help for GUI changes
• UX of all users considered:
  • Speech
  • Braille
  • Low Vision
  • Different web browsers
  • Localization in other languages / culture than English