ENABLE_TOUCH_OPAQUE_ACTIVITIES to default enabled

Try 2, first try broke appcompat post submit tests. No need for the
@ChangeId to be @Overridable on user builds.

Test: atest CtsWindowManagerDeviceTestCases:CrossAppDragAndDropTests
Test: Manually verified that touches are blocked using sample app.
Tested with normal windows, freeform windows and splitscreen
Bug: 194480991
Bug: 215427711

Change-Id: I565698bd93007b4bd6e42f8c8c36732d01c3af11