Checking Launcher internal integrity from tests

In particular, we check that the stable Launcher state equals its
current state. This can help detect Launcher being in a corrupted state
as in b/133867119.

The check gets called by tests when the Launcher is not transitioning
from state to state.

Bug: 137307838
Change-Id: I3d36edff35e42d14be6b9a52351bd6f709be75e8