Partially implement IBC client creation of sovereign rollups on Cosmos chains

[soareschen]

Part of: #10
Prerequisites: #95, #94
also: informalsystems/sovereign-ibc#65

Summary

• In this task we will partially implement the creation of IBC clients on the Cosmos chains.
• The IBC client will be a Wasm client that is compiled from sovereign-ibc to verify Sovereign client updates.
  • The initial implementation will use a pre-compiled Wasm blob that is checked in to the repository.
  • We will automate the build steps of the Wasm blob using Nix in a follow up PR.
• The initial implementation will use a valid Celestia DA header when creating the client.
  • This should be mostly the same as a regular Cosmos client update.
• The initial implementation will provide dummy hashes for the rollup states, and not involved in querying the actual rollup node.
  • The querying of rollup node requires Implement bootstrapping code for Sovereign rollups #94, which will be done in parallel of this PR.
  • Since the aggregate proof system of Sovereign SDK is still being implemented, the validation of rollup state transition is currently mocked in sovereign-ibc.

Implementation Strategy

We will first implement context-generic components that work with a Cosmos chain context, with a Sovereign chain as the counterparty chain. The components would be something like:

pub struct CreateSovereignClientOnCosmos;

impl<SovereignChain, CosmosChain>
    ProvideCreateClientOptionsType<SovereignChain, CosmosChain> 
    for CreateSovereignClientOnCosmos
{ /* ... */ }

impl<SovereignChain, CosmosChain>
    ProvideCreateClientPayloadType<SovereignChain, CosmosChain> 
    for CreateSovereignClientOnCosmos
{ /* ... */ }

impl<SovereignChain, CosmosChain>
    CreateClientPayloadBuilder<SovereignChain, CosmosChain>
    for CreateSovereignClientOnCosmos
{ /* ... */ }

impl<CosmosChain, SovereignChain>
    CreateClientMessageBuilder<CosmosChain, SovereignChain>
    for CreateSovereignClientOnCosmos
{ /* ... */ }

At the end, the SovereignToCosmosRelay context should implement CanCreateClient using CreateClientWithChains, with all its dependencies implemented.

An integration test would be written in the form:

#[test]
async fn test_sovereign_to_cosmos_create_client() -> Result<(), Error> {
    let cosmos_bootstrap = CosmosBootstrap { /* ... */ };

    let sovereign_bootstrap = SovereignBootstrap { /* ... */ };

    let cosmos_chain = cosmos_bootstrap.bootstrap_chain().await?;

    let sovereign_chain = sovereign_bootstrap.bootstrap_chain().await?;

    let create_client_options = SovereignToCosmosCreateClientOptions { /* ... */ };

    let client_id = SovereignToCosmosRelay::create_client(
        DesitinationTarget,
        &cosmos_chain,
        &sovereign_chain,
        &create_client_options,
    ).await?;

    Ok(())
}