Bubble v2 animation improvement.

Including:
1. Add opacity animation when show/hide/expand/collapse
2. Decrease animation duration when hide
3. Animate small icon when switch left/right side instead of changing gravity
Bug: 67605985
Test: manual
PiperOrigin-RevId: 178413027
Change-Id: I8a915bbed60a2841ccc534f2c68575da062c82e3