Make TaskStackListener work in freeform mode

Some callbacks of TaskStackListener aren't invoked in freeform
mode when they should be. For example, currently onFocusChanged()
is invoked in setResumedActivityUncheckLocked(), but this
incorrectly assume that focus change is only caused by an activity
getting resumed.

The main idea of this CL is to move the invocation of some
callbacks from the "caller" of the corresponding event to the
"callee" (or at least a bit deepr in the call stack) to ensure
that we don't forget to invoke them in all cases.

Bug: 268131581
Bug: 268130984
Test: atest CtsWindowManagerDeviceTestCases
Change-Id: I6b0cef7cf14fac161346c88250ab05ea50db6f9a