Add sensor for flip to screen off. See go/flip-to-screen-off-design-doc for design details.

Test: atest FaceDownDetectorTest & Tested with local device.
Bug: 164517126
Bug: 169780171

Change-Id: I7bc634a0ce4b4ae56e017e8cde127cd9c722e0eb
(cherry picked from commit 2be8baec1f0d8bc12758bd671a35e021d6be64bf)
6 files changed