TV: handle PiP density changes

- Makes sure dimensions are reloaded
- Repositions PiP and reloads menu after density change
- Changes PiP menu button padding that was squishing the buttons in some
  cases

Bug: 274750784
Test: manual - open PiP, change screen resolution in display settings
> PiP (including border and menu) should stay the same size relative to
the screen.
Test: manual - open PiP, change density via 'adb shell wm density xxx'
where xxx is a density, e.g. 140 or 340 > PiP should stay the same size,
but border, buttons and distance to the edge of the screen should
change with the density.

Change-Id: I46a5bb6db7c9e54c3d674450b41702e51bdd194b