Only restash TV PiP if necessary on immediate placement

Restricted keep clear area do not immediately move the TV PiP window,
but movements are debounced. But other changes, such as changes to
unrestricted keep clear areas, do cause the PiP to move immediately.
When doing immediate movements, the PiP could stash even though
Placement#triggerStash was not set.

This changes unifies the logic between regular deferred placement and
immediate placement.

Bug: 234421149
Test: atest TvPipBoundsControllerTest
Change-Id: I8cac0ba600f52ff9d72743af2a09eacea4cde629