Change how the ringer drawer background is aligned

The background now has fixed dimentions and is aligned against the bottom right corner of the motion layout instead of the children

Flag: EXEMPT TRIVIAL FIX
Fixes: 428163872
Test: manual on folable. Set display scale to max and compare screenshots with a max scale.
Test: atest VolumeDialogRingerDrawerScreenshotTest
Change-Id: I068301e933e0b05af9ad96c94e479e6d31ba8a5b