Add flag for face message defer logic update

When this flag is enabled, the face message
defer logic will only analyze the last n frames
received by the faceManager rather than analyzing
all the frames to determine whether to show a face
help message on face TIMEOUT

Flag: com.android.systemui.face_message_defer_update
Bug: 351863611
Test: builds
Change-Id: Ifcd37e669ed65128a99cdf9d2d55f17b6bf34591