Add HelloActivity for multi-display test

- Most of code itself is copy of development/samples/HelloActivity with
  package name change.

- MDTHelloLaunchAlways added for documentLaunchMode of always, meaninig it
  is always launched as a new task. This allows multiple instance launching
  in multi-display without requesting app specifying FLAG_ACTIVITY_NEW_TASK.

- MDTHelloLaunchDefault has documentLaunchMode set to default. This activity
  will be started as a new task only when requesting client is adding
  FLAG_ACTIVITY_NEW_TASK flag. Without the flag, the Activity is re-launched
  in a display where it was previously launched. This can be problematic for
  multi-display env if the same app should be used in multiple displays.

Bug: 131628286
Test: Confirm that  MDTHelloLaunchAlways can be launched from each display.
Change-Id: I3fdd92243391ad8efc8908a1600bb3657bdaba55
6 files changed