Initialize display id of fixed rotation listener correctly

- Make sure the listener uses the initialized DisplayContent#mDisplayId.
- Avoid using unexpected member of AppTransitionListener.
  e.g. DisplayContent#mDisplayId will be hidden by
  AppTransitionListener#mDisplayId in FixedRotationTransitionListener
  because the listener is an inner class of DisplayContent.
  So rename to AppTransitionListener#mTargetDisplayId.

Bug: 354626262
Bug: 326610743
Flag: EXEMPT bugfix
Test: TransitionTests
Change-Id: I2d7ca5fdc0a2a468c1d96f2836a11d00714e5e27