support ICS008 wrapper type for host client and consensus state

[rnbguy]

Feature Summary

Now that ibc-go comes with wasm-08, client state of an ibc-rs chain maybe stored as wasm wrapped format in wasm-08 enabled chain.

So when MsgConnectionOpenTry or MsgConnectionOpenAck is received at ibc-rs, it should expect two cases:

1. normal client state. e.g., the chain is using vanilla tendermint engine, so the counterparty ibc-go chain uses ibc-go implementation of ics07.
2. wasm wrapped client state. e.g., the chain is using a custom consensus, so the counterparty ibc-go chain uses wasm client via wasm-08

Proposal

We need to introduce an enum:

pub enum HostClientState<T> {
    Native {
        state: T,
    },
    Wasm {
        state: T,
        checksum: Vec<u8>,
        latest_height: Height,
    },
}

Then, use HosClientState<Ctx::HostClientState> in the following places:

ibc-rs/ibc-core/ics03-connection/src/handler/conn_open_ack.rs

Line 52 in 2378cd4

Ctx::HostClientState::try_from(msg.client_state_of_a_on_b.clone()).map_err(Into::into)?;

ibc-rs/ibc-core/ics03-connection/src/handler/conn_open_try.rs

Line 42 in 2378cd4

Ctx::HostClientState::try_from(msg.client_state_of_b_on_a.clone()).map_err(Into::into)?;

[rnbguy]

Maybe we can add another generic associated type to ValidationContext:

ibc-rs/ibc-core/ics24-host/src/context.rs

Lines 28 to 31 in 2378cd4

	/// The client state type for the host chain.
	type HostClientState: ClientStateValidation<Self::V>;
	/// The consensus state type for the host chain.
	type HostConsensusState: ConsensusState;

    type HostClientStateAtCounterparty<V>: Into<V> + TryFrom<Any> where V: TryFrom<Any>;

And, later, we use it as::

Ctx::HostClientStateAtCounterparty<Ctx::HostClientState>::try_from(
    msg.client_state_of_a_on_b.clone()
  )
  .map_err(Into::into)?
  .into(); 

This way, we allow the crate users to build their own custom host client wrapper.

[rnbguy]

Looks like, the similar is required for host consensus state. In the following, we need to wrap the consensus state in wasm consensus state and then check for proofs.

ibc-rs/ibc-core/ics03-connection/src/handler/conn_open_ack.rs

Lines 119 to 120 in 2378cd4

	let expected_consensus_state_of_a_on_b =
	ctx_a.host_consensus_state(&msg.consensus_height_of_a_on_b)?;

ibc-rs/ibc-core/ics03-connection/src/handler/conn_open_try.rs

Lines 115 to 116 in 2378cd4

	let expected_consensus_state_of_b_on_a =
	ctx_b.host_consensus_state(&msg.consensus_height_of_b_on_a)?;