Better IBC client entry points

[larry0x]

Currently, the IBC client entry point looks like this:

#[entry_point]
fn ibc_client_create(
    ctx: MutableCtx,
    client_state: Json,
    consensus_state: Json,
) -> Result<Response>;

Inside the function the developer needs to manually deserialize the Jsons. Ideally we do this in the #[entry_point] macro, so that the function signature becomes:

#[entry_point]
fn ibc_client_create(
    ctx: MutableCtx,
    client_state: ClientState,
    consensus_state: ConsensusState,
) -> Result<Response>;

where ClientState and ConsensusState are arbitrary types defined by the developer.

[larry0x]

Not planned any more. There won't be an ibc_client_create method. Just use instantiate.