Show overview as grid in fallback recents

- Replace mShowAsGrid with state specific mOverviewGridEnabled and mCurrentGestureEndTarget
- Avoid showing invisible home task in grid
- Fix quick switch out of orientation in fallback recents
- Add a HOME state to switch to when starting home, to avoid showing grid overview briefly in quick switch
- Separate clear all button and overview actions handling
- Always maintain first task's fullscreen translation at 0 to avoid jumping when mOverviewFullscreenEnabled changes
- Moved fullscreenTranslation calculation to RecentsView
- Added GestureEndTarget -> BaseState translation to allow querying displayOverviewAsGrid for a displayOverviewTasksAsGrid

Bug: 174464863
Test: Launch overveiw from home, launch overveiw from app, launch into app, test for both small and large screens
Change-Id: Iee06d94d3067ea45cadd2051717223ddc0e6e70c