Fix RTL TV PiP position

Gravity.END doesn't seem to work, even when adding the correct layout
direction to Gravity.apply(...). Therefore manually check for RTL and
using left and right gravities.

Bug: 245290804
Test: atest TvPipGravityTest
Test: manual - change system language to RTL language e.g. Arabic, start
regular PiP + start expanded PiP and collapse via menu -> PiP should be
in the bottom-left corner

Change-Id: Id8fb19271d6b31515420b298693cb5eb01678c44