SystemUI: QS Details: Fix layout issues

* Remove bottom padding:
  * It shifts the content up unnecessarily
  * It leaves a small white line at the bottom
* Introduce a new background color for the switch bar: derived from
  textColorPrimary because that is basically the exact opposite of the
  background color so it allows us to get a slightly brighter overlay
* Also change the qs detail's background: use the same color as for the
  rest of the qs backgrounds - now it doesn't look different from the rest
  anymore (was a slightly darker shade of white on light theme and a
  brighter grey on dark. This was more noticeable on a dark theme and is
  basically also the reason that we noticed the wrong padding
* For zen tile (dnd), remove all background color references and apply
  qs_background_primary for the whole panel at once. Applying the
  color manually is required because the panel is inflated separately
  and not using the color that is assigned to the original content.
  Removing all separate references allows to define and change the color
  in one place
* In order to make the buttons also look good on dark background,
  assign a color (similar to the one for the switchbar, see above)
  manually
* Also remove the min height and add top/bottom paddings so the buttons
  are not as huge as currently
* Remove start and end padding from QS detail header xml, because they are
  a) a mixture of left and end, which should really be start/end or
     left/right
  b) Not used anymore, as QSDetail.java applies them in
     onApplyWindowInsets programmatically

The alpha values of 5% and 8% for our newly defined colors were determined
by trying various values until it looked good on all themes

Test: Open every qs tile on both light and dark themes and see if
 they look proper

Change-Id: I5be8bf97582e877bdb1af1f3aedc88c00d134c16
8 files changed