Improve stack selection logic during adjacent launch

Adds handling for some cases when activity is launched with flags
FLAG_ACTIVITY_LAUNCH_ADJACENT and FLAG_ACTIVITY_NEW_TASK.

- If target activity is not in focused stack - use current
  parent stack.
- If target activity is already on top of focused task - use
  focused stack.
- If task is in focused stack but not on top - move to adjacent
  stack.

Bug: 27729085
Change-Id: I2041a46056f880dc0ff61b2b7c384c7297a69479