[PiP2] Don't update display layout for same id

When getEnterPipTransaction() is called to get the WCT
we should only update the display layout if the task's displayId
is different from the cached one.

Bug: 394931678
Flag: com.android.wm.shell.enable_pip2
Test: swipe up to enter PiP from landscape mode
Change-Id: I0e4364b04218bd3ebc5ce9692e2791ae917844e7