Validate user on biometric auth and keyguard done

On user switching, it is possible to start a chain of events
that validate the prior user before user switching is complete,
notably on biomtetric auth success and the tryKeyguarDone paths.
The latter is a runnable that can be scheduled after dismiss
animations run, but if the user was changed in the middle, it
is possible to dismiss the prior keyguard.

Revalidate the user at multiple points, and reset the keyguard
when the user id mismatch is detected.

Bug: 413380719
Test: atest KeyguardViewMediatorTest
Flag: EXEMPT bugfix
Change-Id: I70efe8704931e096698d4a775ee487bb5241d7f1