WindowOrganizerController: Correct task insets for non-fullscreen windows

Ensure correct insets are applied to windows that are not fullscreen and have a height different from the display. The task insets mOffsetYForInsets is now recalculated in `applyTaskChanges` to address this.

Bug: 402658128
Flag: com.android.wm.shell.enable_flexible_two_app_split
Video: http://recall/-/gvQq7Z7JECwxnxKrBmr3wt/eJyJZAXioJImmTYc4GD492
Test: manual test.
Change-Id: Ic4c67eba53ad2ef1b0b6870b3e9f8f5920c8d834