Add nice animation when adjusting for IME in multi-window

- Run a separate animation when we need to adjust for the IME. We
can't use the attached animation because the adjustment animation
needs to be longer than the IME animation.
- Also run an animation when IME is disappearing.
- Adjust IME exit animation to better match with adjustment exit
animation.
- Make sure to update adjust for IME when entry/exit animation of
IME is starting, to avoid flickers.
- Don't update the IME window in PhoneWindowManager for layout
until the animation has started. This lead to an issue where the
content inset was set too large too early.

Bug: 27154882
Bug: 28175599
Change-Id: I09a33413e307f84d6c3cf4ae928c280f7ad48348