Bug fixes and cleanup

- Don't reinflate the search bar view every time you return to recents
- Fixing an issue where the default thumbnail was not being used when querying the thumbnail cache (thought WM still seems to not be giving us screenshots in many cases)
- Fixing an issue where an invisible header bar color was used instead of the default header bar color
- Fixing an issue where swipe-to-dismiss logic was running before the animation back into place
- Using outline clipping instead of doing it ourselves for the rounded TaskView
- Small optimization in finding the visible range
- Renaming some of the callbacks to make them more clear
- Removing some unused code