Prepare to remove new headers flag

This CL sets everything up for removal of the flag. In particular:

* Shortcircuits any conditional the flag was in to true.
* Removes all the header views and code from QuickStatusBarHeader and
  controller. This still exists because it contains QuickQSPanel and
  refactoring is outside of the scope of this CL.
* Renames LargeScreenShadeHeaderController to ShadeHeaderController
* Replaces the view with a MotionLayout unconditionally
* Removes dimens that were explicitly for combined headers and applies
  them to the default dimen.
* Combines LargeScreenShadeHeaderControllerTest and
  LargeShadeHeaderControllerCombinedTest into ShadeHeaderControllerTest
* Adds the views to the NotificationPanelUnfoldAnimationController

Bug: 254512321
Test: SystemUITests
Test: QS PlatformScenarioTests
Change-Id: I578b82571dc91a9e31c196f3affe60d84c64a1fe