Fix 4691563: Polish MultiWaveView experience in LockScreen and InCall screen

Better activation experience:
	- Hold off on switching out targets until current animation has finished.
	- Hide unselected targets when a target is selected.
Code simplification:
	- Use explicit callback objects to handle animation updates instead of having MWV implement the interface.
 	- More compact chevron-loading code.
	- Don't use animations for properties that need to change immediately.

Other minor timing tweaks.

Change-Id: I328533e8ab7b4c69c7ba51c8c55002765dcbbd46