Camera: allow external devices to face backwards

The Camera1 API does not support external camera devices, so the
API1 shim exposes external camera devices as front-facing. This
causes the image to be mirrored for Camera1 applications only,
which is not always desirable.

Allow external camera devices to be back-facing.

Bug: 173800314
Bug: 173208517
Test: atest android.hardware.camera2.cts.CameraManagerTest#testCameraManagerGetDeviceIdList
Test: atest android.hardware.camera2.cts.ExtendedCameraCharacteristicsTest#testLegacyCameraDeviceParity
Test: atest android.hardware.cts.CameraTest
Test: atest android.hardware.multiprocess.camera.cts.CameraEvictionTest#testMediaRecorderCameraActivityEviction
Change-Id: I4af5bf684a0ee7ca0e4d1d5cfadc50e4ee650702
(cherry picked from commit 562289ce2b05a8fb48cf6ac3308c9f32d5da89a2)