Implement serde_with::SerializeAs and serde_with ::DeserializeAs for ArrayVec

[kraktus]

serde_with is a widely used crate (24M downloads) to allow custom (de)serialisation.

This commit allow to use Arrayvec as a container in the serde_with::serde_as macro.

#[serde_as]
#[derive(Serialize, Deserialize)]
pub struct Native {
    #[serde_as(as = "ArrayVec<DisplayFromStr,128>")]
    pub sans: ArrayVec<TypeWithoutSerde, 128>,
}

I've it included under the serde feature, but it can be on its own feature.

If this is deemed to niche to include, an alternative would be to include it directly in the serde_with crate under a feature flag, similar to what is done for other popular library, such as hashbrown_0_14 or chrono_0_4. It has the disadvantage of pinning to one version.