Slightly improve Taskbar animations to launcher

- Move Taskbar scale to LauncherState
- Rename TaskbarVisibilityController to TaskbarAnimationController and
  add mTaskbarScaleForLauncherState to TaskbarAnimationController
- Set OverviewState#getTaskbarScale() = 1f so Taskbar doesn't scale
  up when going from an app to Overview
- Increase home animation duration so Taskbar animation aligns better

Test: Taskbar scales up when going home, doesn't scale up when going
to overview
Bug: 182512211

Change-Id: I6f448e76de98d7ff337ae93234d4bb7ce6254d50