Mobile: Fixes #9858: Fix deeply-nested subnotebook titles invisible in the folder dropdown

[personalizedrefrigerator]

Summary

Limits the maximum indentation depth in the note list to 2/3rds of its width. This ensures that at least part of a notebook title is visible.

Fixes #9858.

Screenshot

Testing

1. Create a large number of nested subnotebooks
2. Open a note and change its parent notebook using a dropdown
3. Rotate the phone and repeat steps 1-2. Verify that the maximum indentation is larger when the screen width is larger.

This has been tested successfully on Android 7.