Enable variable size thumbnail for large screen

- Introduced a feature flag
- Refresh TaskView size when thumbnail is refreshed or Recents resizes
- Disable edge scale down in large screens
- Added temp method to get task width/height ratio
- In fullscreen, scale down TaskThumbnailView and disable TaskView elevation
- Task boxing mechanism: http://screen/3NkePthAVUVH2Rv.png

Bug: 174464656
Test: Manually test overview and quickswitch for folded and unfolded, including with RTL.
Change-Id: I2ce24d588a246cc6a2408039a37d884021aa0800