Integrate ICS02Client into ICS26Router to Enable Client Updates in Multicall

[srdtrk]

Summary

Currently, update client calls cannot be included in a multicall to the ICS26Router, which complicates relayer interactions. This issue proposes merging the ICS26Router and ICS02Client to streamline these operations.

Problem Definition

A relayer should only need to interact with the ICS26Router contract. Presently, to independently update a client, the relayer must interface with ICS02Client, and critically, cannot perform this action within a multicall.

Use cases

Enables relayers to include client updates within multicall messages, reducing the need for multiple contract calls.

Proposal

Integrate ICS02Client functionality into ICS26Router by converting ICS02Client into an abstract contract, simplifying relayer interactions and enhancing multicall capabilities.