Improve floating keyboard mode

[Mokhyy]

Feature request:

I’d like to suggest a few improvements for the floating keyboard mode.

I found two keyboards that implement floating mode well without requiring the display over other apps permission:

• HeliBoard (new version): floating mode works very well and includes floating keyboard resizing
  Add floating keyboard HeliBorg/HeliBoard#2501

• HoneyBoard: also supports floating mode without this permission and works smoothly
  https://codeberg.org/propagandalf/HoneyBoard

Suggested improvements

1. Change the floating-mode implementation
   Replace the current floating implementation with an approach that does not require the display over other apps permission.
   HeliBoard and HoneyBoard could be used as references for this.

2. Change the behavior of the × button
   The current × button returns the floating keyboard to normal mode.
   Instead, it should only close the floating keyboard while keeping floating mode saved.

3. Persist floating mode state
   Save the floating keyboard state so that floating mode is enabled by default the next time the keyboard is opened.

4. Add floating keyboard resizing
   Add support for resizing the floating keyboard, similar to HeliBoard.

5. Move the drag handle
   Move the keyboard drag handle from the top of the keyboard to the bottom.