Launch 2D activities in VR mode

When in VR mode, launch all activities into the virtual display ID as
provided by the Compatibility display. This includes two cases -

- New activity launches
- Existing activity in the background.

Testing Done: Tested with PlanarVirtualDisplay app and Settings,
Calculator and GestureApp with different intent flags.

Bug: 36071574
Bug: 36071445
Test: android.server.cts.ActivityManagerDisplayTests
Test: #testVrActivityLaunch
Test: #testVrActivityReLaunch

Change-Id: Ic590a7cbd6f9b339dc83b22a8ffb1252219ef22e
Signed-off-by: Karthik Ravi Shankar <karthikrs@google.com>