Function spill_serialized 

fn spill_serialized<C: Columnar>(
    body: &ColumnBody<C>,
    pool: &Pool,
    len_bytes: usize,
    hints: ChunkHints,
    codec: &'static dyn ExtentCodec,
) -> ChunkHandle

Serialize a body into a pool slot, writing its serialized form through a cursor over the slot memory. A serialized body’s encoding is one copy. Sizing is exact, so a short or overlong write is a contract violation and panics.