Limit Volume Dialog window width

The gpu memory buffer is allocated for the whole size of the window
regardless of it being mostly transparent. This is a huge waste of
resources given that the Volume Dialog only occupies a small fraction of
it.

We still want to fill the whole height though because of the animation
around half folded internal screen on a foldable device.

This CL introduces a compromise betwee precise control over Volume Dialog vertical alignment and window size.

Flag: com.android.systemui.volume_redesign
Fixes: 398311439
Test: atest VolumeDialogScreenshotTest
Test: manual on foldable. Observe volume dialog appearance. Check that
there is enough space for the horizontal ringer drawer.

Change-Id: Ia8b1fe90ed59b32b7e1412074a52c44648ac7927