Serialized Any does not have type field

[iboss-ptk]

When Any type gets serialized, it removes @type field due to current limitation of https://github.com/CosmWasm/serde-json-wasm. It does not implement serialize_map (which serde-json-core does).

That means we can't implement type:

#[derive(Clone, PartialEq, Eq, Debug, Serialize, Deserialize)]
pub struct AnyT<T>
where
    T: Serialize + DeserializeOwned,
{
    pub type_url: String,
    #[serde(
        flatten,
        serialize_with = "T::serialize",
        deserialize_with = "T::deserialize"
    )]
    pub value: T,
}

Which can produce serialization that looks conform proto json format.

{ "@type": "<type_url>", ...<struct_fields> }

Current implementation for serde_json_wasm will panic due to calling unreachable!().