[Android] - Toast appears below Modal

The below screen recording demonstrates the bug reproduction.

https://user-images.githubusercontent.com/23293248/129330590-4eff19d3-2f8a-4e72-8526-08044876c158.mov

## Reason
On Android, we're using RN's Modal to show the Overlay instead of using OverlayContainer. This has been done for accessibility reasons (to auto-shift focus when opened). This is leading to the below issue. RN's Modal has the highest precedence and it won't let any absolutely placed View appear on top. A quick fix would be to replace RN modal with OverlayContainer and shift focus manually.