Add multi-user jank monitoring

Created CUJ for monitoring jank when switching users, including guest
users, but excluding the "Add User" user journey.

Bug: 200160966
Test: switch users manually, look at logs
Test: atest KeyguardUpdateMonitorTest
Test: atest UserSwitcherControllerTest
Change-Id: I5570133a1f96a58d39a8f053f9f480cdaada8df1