Move the Tv volume dialog to a vertical layout

The CL sets the gravity of the volume dialog for TVs to
RIGHT|CENTER_VERTICAL.

It does the following:
1. Remove unnecessary margins and paddings in volume_dialog.xml, which
were either meant for phones or for the previous horizontal layout. The
new layout is generic and can be used both for horizontal and vertical
volume dialogs.
2. Adjust the elements in volume_dialog_row to the right,vertical ui

Bug: 162302410

Test: m && flash && verify that the volume ui is vertical
Change-Id: If55413f8c3ade1dcda594bcb765fa0ee9e30ee08