pub fn read_layout_from_initial(
    initial_read: &InitialRead,
    layout_serde: &LayoutDeserializer,
    scan: Scan,
    message_cache: RelativeLayoutCache,
) -> VortexResult<Box<dyn LayoutReader>>pub fn read_layout_from_initial(
    initial_read: &InitialRead,
    layout_serde: &LayoutDeserializer,
    scan: Scan,
    message_cache: RelativeLayoutCache,
) -> VortexResult<Box<dyn LayoutReader>>