Restore all user visible tasks on user switch.

Also make sure that there is only one entry for tasks being added for
non-current users.

Test: Manually test that an activity that's marked as visible for all
users and runs on User 0, is restored on user switch if it's also
visible previously.
Test: atest RootWindowContainerTest
Bug: 381038076
Flag: com.android.window.flags.enable_top_visible_root_task_per_user_tracking

Change-Id: Ibfa050915a354b7a31e63bcb1f2c510203a0d2f7