Add CAMERA_COMPAT_FREEFORM_UNSPECIFIED type.

This is to map FreeformCameraCompatMode to atom enum values (which should
 have an unspecified value with tag 0) and therefore make logs processing
more readable.

Flag: com.android.window.flags.enable_camera_compat_for_desktop_windowing
Test: atest WmTests:CameraCompatFreeformPolicyTests
Bug: 383981634
Change-Id: I225f4371c11c74fdfcb9a53062677eb3e36e1a19