Use Choreographer from ViewRootImpl

This change adds a method to retrieve the choreographer instance that is
tied to the ViewRootImpl. It also updates JankTracker to use that
instance instead of using the global choreographer instance. This should
ensure the vsync ids we are using to keep track of active states line up
with the ids that are being returned by OnJankDataListener.

With this change the instantiation of StateTracker and JankDataProcessor
are now delayed until after the OnWindowAttachListener is invoked. This
was required as the DecorView still returns null when calling
getViewRootImpl while JankTracker is instantiated within the Activity.
StateTracker has a dependency on Choreographer so an active instance of
ViewRootImpl is required to obtain that.

Change-Id: I41728d4488bfb2df7d3c355ff8713cc673d13fc8
Bug: 377960907
Test: atest CoreAppJankTestCases
Flag: android.app.jank.viewroot_choreographer