Chore: Reduce mobile note screen test flakiness

[personalizedrefrigerator]

Summary

This pull request attempts to fix CI failures related to recent changes to mobile tests. These failures seem related to the recent switch to fake timers in screens/Note.test.tsx. This pull request attempts to enable fake timers only for the parts of the tests that relate to performance, while preventing test warnings that were previously resolved by switching to fake timers.

Notes

• When state changes aren't wrapped in act (or waitFor, or certain react-native-testing-library queries) during testing, react-test-renderer (used by react-native-testing-library) produces a warning. Several added waitFors and acts are intended to prevent warnings related to background state changes.
  • One example of this is the check that the menu component has finished moving focus to itself before continuing — the focus change is caused by a delayed state change.