ICS2: Split checkValidityAndUpdateState into 4 functions

[colin-axner]

In ibc-go, we have decided to refactor the 02-client submodule along with the interfaces defined within the ClientState. One of the decisions made was to split the checkValidityAndUpdateState into 4 functions:

• VerifyClientMessage
• CheckForMisbehaviour
• UpdateStateOnMisbehaviour
• UpdateState

Part of the reasoning for this change was that checkValidityAndUpdateState began to become overloaded with functionality as it was required to account for misbehaviour detection as well, which may not be apparent to light client developers, so a more explicit API requiring misbehaviour detection seems ideal. Since the entry point to updating a IBC client now accounts for misbehaviour detection, it made sense to combine these interfaces so any sort of update (misbehaviour, normal updates, batch updates) could use the same API

references

discussion leading to design
ibc-go issue