Update user event listeners

UserGridRecyclerView doesn't need to be registered to so many user
change events.  This CL cleans up that list.

Bug: 142019015
Test: atest CarSettingsRoboTest
Test: Manually add/remove users and switch to users/guest from quick
settings user picker

Change-Id: Iff417591cf2d91add30bdb40881f6c504344b0ee