Mobile: Fixes #10253: Move accessibility focus to the first note action menu item on open

[personalizedrefrigerator]

Summary

This pull request fixes #10253 by moving focus from the note action menu toggle to the first item in the note action menu when the menu opens. To simplify this, the popup menu code is moved to a separate file.

See also #10333.
Edit: Related to #11661.

Testing plan

Existing tests that apply to this pull request:

• screens/Note.test.tsx: Verifies that the menu can be opened and items in the menu can be activated.

Manual testing:

• Web (Firefox):
  1. Navigate to the note action button with tab.
  2. Press enter.
  3. Verify that the note action menu is visible.
  4. Navigate to the "tags" button by pressing tab.
  5. Verify that the tab order was "Attach", then "Draw picture", then "Tags".
  6. Press enter.
  7. Verify that the menu opens.
• Android 13:
  1. Enable TalkBack.
  2. Move TalkBack focus to the note action menu button.
  3. Navigate to "voice typing".
  4. Verify that the focus order is "Attach" > "Draw picture" > "Share" > "Voice typing...".
  5. Activate "voice typing" by double-tapping.
  6. Verify that the menu closes.
     • Follow-up issue: Focus jumps to the first item in the note. The voice typing heading should auto-focus.