Allow IMMS to switch to an "always visible" user profile

Profiles with "getAlwaysVisible" set should be able to show UI even when
they are not in the foreground, and/or do not have the current user as a
parent. This CL includes always visible profiles for cross-profile
switching.

Bug: 389712089
Test: atest
FrameworksMockingServicesTests:com.android.server.pm.UserManagerServiceMockedTest
Flag: android.multiuser.allow_supervising_profile
Change-Id: If2b77ab05f4899c79e9c749a98fc976bad12f5ce