Make Volume Dialog slide espite current screen orientation

This CL also fixes positions for the floating sliders in RTL layout.
We always want the dialog to be on the right side of the screen next to
the volume buttons despite the layout direction.

Flag: com.android.systemui.volume_redesign
Fixes: 267682354
Test: manual on foldable
Change-Id: I58eceac32c020fbe64409786eb77780d4b27c136