Add RTL support for A11yMenu ViewPager.

When in RTL languages, reverses the direction of the left & right buttons.
Demonstration video: https://x20web.corp.google.com/users/jo/jonesriley/fabFootage/viewPager2.mp4

Bug: 279191187
Flag: EXEMPT internal refactoring
Test: atest A11yMenuServiceTests
Change-Id: I9626f504a444928d717f3f9b03600d7058203c78