SystemUI: improve tile caching mechanism

- Always remove all tile views before setting new tiles

- Save and restore the viewpager page when setting tiles as we need to
  reset this page when we're done (after re-setting the adapter)

- Reset the pager adapter to force page removes and fix ghost scrolling
  to non existent pages.

- No need to set tiles to 0 while recreating status bar or switching
  themes

- Always recalculate heights after switching brightness slider, and
  explicitly set the visibility on the slider too

Ref: CYNGNOS-1644 OPO-367

Change-Id: Id08fbbcd38f24c16ee044c0d63389b36845c81b9
Signed-off-by: Roman Birg <roman@cyngn.com>