Add API for expanded picture-in-picture

Bug: 208797488
Test: atest PinnedStackTests#testEnterExpandedPipAspectRatio
Test: atest PinnedStackTests#testEnterExpandedPipAspectRatioMaxWidth
Test: atest PinnedStackTests#testEnterExpandedPipAspectRatioMaxHeight

Change-Id: I7d91ce1db197cf7dac1af8bdf4ee2579b8a70869
4 files changed