Add some tests for freeform stack.

- Verify we can enter freeform mode on devices that support
PackageManager#FEATURE_FREEFORM_WINDOW_MANAGEMENT and the
opposite on devices that don't support the feature.
- Verify that ActivityOptions.setLaunchBounds works correctly
when we are in freeform mode.

Bug: 27157914
Change-Id: I679d93f9365be77b2f772a3d450b603efd5f9f5a
5 files changed