Move and clarify the native word math support option (#19926)
### Summary of the issue:
The "Use native math speech in Word and Outlook" option is misleading,
as it affects speech, braille and navigation.
### Description of user facing changes:
The option has been renamed to "Use native math support in Word and
Outlook", and moved to a new "Application support" section of the Math
settings panel.
The user guide has also been updated to clarify how the option works,
and that this prevents using MathCAT in Word and Outlook altogether.
### Description of developer facing changes:
None.
### Description of development approach:
Created a new group in the math panel. Moved the checkbox creation after
creation of that panel, and changed it to point to the new group.
Rewrote the UG as appropriate.
### Testing strategy:
Ran from source and checked that the settings panel looks correct.
Built the user guide from source and checked the output.
Ran from source, tabbed to the native word math checkbox and hit `F1`
and checked that I was moved to the correct section of the user guide.
### Known issues with pull request:
None
