Update user switching processes

Add a new callback for UserController. If the user is secure, initiate
a call to SystemUI to lockNow(), and wait for the callback. If the
callback does not arrive, crash the system after some time.

During user switching, ensure that systemui locks the device immediately
if necessary and cancels any prior attempt to dismiss.

Also, ensure that any switch is user that occurs after WM has been
notified that SystemUI is going away is stopped.

Bug: 322157041
Test: atest KeyguardViewMediatorTest
Flag: EXEMPT bugfix
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:15c517ef199695c24560aa5f6b28c374ed111d68)
Cherrypick-From: https://googleplex-android-review.googlesource.com/q/commit:b206e3a5d05e943f2c4c4d36c0b83418b4f18949
Merged-In: I32699e32fe1dbe94af2abe7e7ade5363a2b6cb55
Change-Id: I32699e32fe1dbe94af2abe7e7ade5363a2b6cb55