Add test for creating dummy rollup client on mock Cosmos chain

[Farhad-Shabani]

Summary

This task involves enabling the rollup to introspect itself and query its own consensus state. However, the structure of the rollup’s consensus state is unclear at the moment (blocked by #7).
But, in any case, considering Celestia as our first target DA layer, we might use a dummy Tendermint client for the rollup on the mock Cosmos chain with an intermediary implementation for the host_consensus_state method.
This task is necessary for establishing clients on both mock chains and preparing for the subsequent step, which involves updating the rollup's client on mock Cosmos.