Mobile: Accessibility: Improve setting control accessibility

[personalizedrefrigerator]

Summary

This pull request should improve the accessibility of controls in the mobile settings screen. In particular, it:

1. Associates labels with text inputs using aria-labelledby.
   • It doesn't seem possible to do this with sliders/switches in React Native.
2. Adds labels to dropdowns and switches using accessibilityHint.
3. Replaces settings-related usage of role= with accessibilityRole=. On Android, the role prop seems to have no effect (where the accessibilityRole prop does).
4. For screen readers: Marks the selected item in dropdowns as selected.

Testing

Manual testing plan

Android:

1. Open settings.
2. Enable TalkBack.
3. Open the "general" tab.
4. Focus the "date format" dropdown.
5. Verify that TalkBack marks the dropdown as a "button" and reads the label associated with the dropdown.
   • Previously, the dropdown was not labelled with a role.
6. Open the dropdown.
7. Verify that the selected item has accessibility focus.
8. Swipe to the next item.
9. Swipe to the previous item.
10. Verify that TalkBack reads the last-selected item as "selected".
11. Close the dropdown by selecting an item.
12. Move accessibility focus to the "automatically delete notes in the trash after a number of days" switch.
13. Verify that TalkBack reads the switch label when the switch is focused.

• Previously, the label was not programatically associated with the switch. With this pull request, the label is associated using accessibilityHint — associating the label with aria-labelledby doesn't seem to work.

14. Switch to the "Note" tab
15. Focus the "Voice Typing language files" textbox.
16. Verify that TalkBack reads "Edit box for Voice Typing language files (URL)"

[personalizedrefrigerator]

I'm linking this to #10795.