Allowing Launcher to draw behind cutouts

> Launcher uses realSize, availableSize and insets to calculate
various layout values. Without drawing behind cutouts, these values
are not consistent (insets + availableSize != realSize) leading to
jumps in layouts.
> Removing fake black bars in low-ram devices to avoid inconsistent
insets.
> Fixing various layouts not taking lert/right insets into account.

Bug: 156268804
Change-Id: I8441db8a468b08a65b57b932050b5b4b37313966