Introduce android.anim thread in system_server

We create a new thread on which everything is running that
directly impacts window animations, i.e. layout, anim tick and
starting window creation. This is such that any work on
android.display can not lead to jank in the window animation,
specifically lock contention on activity manager lock that blocks
callbacks from android.display into AM can not lead to window
animation jank.

Test: Run animation, take systrace, make sure animation is on
android.anim
Test: AppWindowContainerControllerTestTest: AppWindowContainerControllerTestss
Fixes: 36792959

Change-Id: I5d41419a709b7984724e7053a3afdcc1ffe1aaa2