SystemUI: fix qs tile page regressions

- Hide QS tile toast message while adding tile

- Don't allow scrolling right when on last page

- The viewpager adapter is no longer responsible for actually creating the
  backing pages, so we can safely cache them and add/remove them as the
  viewpager sees fit. The pages will be permanently cached until a
  future call to setTiles() results in less tiles, and the page will be
  automatically cleaned up.

- This also fixes no tiles after theme change

- And resetting tiles too, custom tile listeners were interfering and
  overwriting the default tile values

Ref: CYNGNOS-1644

Change-Id: Ibb43adb249b81601370ceab4a4873f91b34b5074
Signed-off-by: Roman Birg <roman@cyngn.com>