Calculate KCA Rect once PiP consistent

Display bounds are updated as we are entering
PiP in fixed rotation. This means if KCA updates come in
before PiP is in a consistent state, we can be left with
an incorrect offset during fixed-rotation enter PiP in btn nav.

Bug: 377372720
Flag: com.android.wm.shell.enable_pip2
Test: enter PiP in fixed-rotation in button-nav mode
Change-Id: Ie1494190dc6c88e1e9a394ea971d411852ce79eb