[PiP on Desktop] Make inset update a Transition if changing app bounds.

Recall: http://recall/clips/b59c5f39-d227-40e7-ac70-f5ef7b68a9b6

This is a quick fix for b/407880128 - making the inset update a
Transition will prevent a race condition that causes the inset update to
not come in time sometimes when expanding from PiP to freeform. When
this happens, multi-activity PiP (e.g. Netflix) will not be inset from
the caption correctly, causing the app content to be behind the caption
bar.

A follow-up CL will fix the animation so that the jumpcut doesn't happen
when the caption bar comes in.

Bug: 407880128
Test: atest DesktopModeWindowDecorationTests
Flag: com.android.window.flags.enable_desktop_windowing_pip

Change-Id: I3e17a0ac4c030fae0f3f0003218e1342334465a2