Support TermId (de)serialization to/from sequences

[ielis]

Allow TermId (de)serialization to/from Ts that implement IntoIterator<TermId> or FromIterator<TermId>.

For instance, a Feature with an iterable field, such as alt_term_ids, can now be serialized:

#[derive(PartialEq, Debug, serde::Serialize, serde::Deserialize)]
struct Feature {
    #[serde(
        serialize_with = "TermId::serialize_as_curie",
        deserialize_with = "TermId::deserialize_from_curie"
    )]
    term_id: TermId,

    #[serde(
        serialize_with = "TermId::serialize_as_curie_seq",
        deserialize_with = "TermId::deserialize_from_curie_seq"
    )]
    alt_term_ids: Vec<TermId>,
}