Refactor to use the PipContentOverlay

Use the same PipContentOverlay in Launcher as in WMShell, this should
further make it easier to experiment the app icon overlay (solid
background with app icon as an overlay).

Bug: 265998256
Test: Enter PiP from Google Maps, ensure the content overlay works
Change-Id: I1ce008700da44bdc28b9515e03aeb3c9c9633f59
1 file changed