Make sure Tiling knows when a task is focused

Currently, if the task gets the focused from the `moveToFront` method in
`DesktopModeWindowDecorViewModel`, the task info hasn't been updated
with the focus information yet, so the tiling thinks that task lost the
focus. Coupled with the fact that the signal from the focus listener
seems often lost, we often didn't know the tiled tasked had the focus.

Fix: 378129032
Flag: com.android.window.flags.enable_tile_resizing
Test: atest DesktopTilingWindowDecorationTest
Test: Manual test on Pixel tablets
Change-Id: I4d70074939aa4926b5e1b3c2d94c745dcd353838