Debounce TV PiP movements

To prevent erratic movements of the TV PiP window, this change causes
changes to the PiP window position to be delayed by 300ms. Only if the
target position of the PiP stays uncontested for that time will the PiP
actually move there.

Bug: 226583836
Test: atest KeepClearRectsTests
Test: TvPipKeepClearAlgorithmTest TvPipBoundsControllerTest
Change-Id: I8e8736fc26b2382b8e540be82d335e0b00a3c62a