Generics support for QueryResponses derive macro

[CyberHoward]

Currently the use of generics in query endpoint messages are not supported by the #[derive(QueryResponses)] macro.
By supporting generics in QueryMsg definitions developers can more easily modularise their smart-contracts.

Example:

#[cosmwasm_schema::cw_serde]
#[derive(QueryResponses)]
#[query_responses(nested)]
pub enum QueryMsg<BaseMsg, AppMsg = Empty> {
    /// A configuration message to a base implementation.
    Base(BaseMsg),
    /// Custom query
    App(AppMsg),
}

[uint]

I just checked and yeah, generics work for QueryMsg generally, but not when the QueryMsg is nested. Looking into it.