Function field_diff_into_proto

fn field_diff_into_proto<K, KP, V, VP>(
    field: ProtoStateField,
    diff: &StateFieldDiff<K, V>,
    writer: &mut ProtoStateFieldDiffsWriter,
)
where
    KP: Message,
    K: RustType<KP>,
    VP: Message,
    V: RustType<VP>,