Make getAliveUsers() and getUsers() as @TestApi.

To replace deprecated UserManager#getUsers(boolean, boolean, boolean),
which is used in CTS, we need to make the alternative methods Test API.

Bug: 253528462

Test: atest UserManagerTest BackgroundActivityLaunchTest

Change-Id: I07b356d210661fe1e0231a7d0aa6b061af032f04
2 files changed