Rename `SEQ_EDIT_OVERLAY_SHOW` to `SEQ_EDIT_USE_FRAME_OVERLAY` to avoid confusion between `SEQ_SHOW_OVERLAY` of `SpaceSeq.flag`
Rename `SEQ_EDIT_OVERLAY_SHOW` to `SEQ_EDIT_USE_FRAME_OVERLAY` to avoid confusion between `SEQ_SHOW_OVERLAY` of `SpaceSeq.flag`