Put PiP layer behind input consumer when resize

Put PiP layer behind input consumer in z-order when resize happens,
the input events would go into the app otherwise.

Flag: com.android.wm.shell.enable_pip2
Bug: 415904533
Test: Manually, tap with one finger and quickly try to move with the 2nd
Test: atest com.android.wm.shell.pip2.PipSurfaceTransactionHelperTest
Change-Id: I0a0925c2d817954677491ab289134c67dd8280a1