Request transition when PIP is removed

This CL is a reland of the following change with a fix for CTS:
I4c13ecc1b3c1dff15bd0d61aeafeacc1d7705460

Original commit message from here

When PIP gets killed via removeRootTasksWithActivityTypes(), no
transition is requested. For non-PIP tasks, processRemoveTask()
is called to remove the task, in which
requestCloseTransitionIfNeeded() is invoked.

But in the case of PIP, removePinnedRootTaskInSurfaceTransaction()
is called but we seem to miss requesting a close transition.

Original commit message to here

The original change broke a CTS test, which expects onStop() is
called before onPictureInPictureModeChanged() when PiP is removed.
This is because scheduling a transition at the beginning of
removePinnedRootTaskInSurfaceTransaction() prevents the workaround
of forcefully stopping the PiP activity in the same function from
working.

The reason why the workaround doesn't work is, in
processStoppingAndFinishingActivities(), there's a check whether
a stopping activity is in a transition, and if it is, stopping it
is deferred.

However, we need to start a transition before we forcefully make
the activity invisible and stopped to properly collect it, so
this CL gives an exception to forcefully hidden PiP so that
it will be stoppped immediately even if it's in a transition.

Bug: 277864359
Bug: 275021556
Bug: 273141544
Bug: 272637936
Test: PinnedStackTests
Change-Id: Iec89dcdd0081eca1f26161aaead1662f0f661ab6