Remove a patch that overrides ValidateSelfClient

[bluele]

Currently, in a chain that has a client, which uses the proxy, the self clientState needs to be unwrapped to the underlying client state with ValidateSelfClient.

This can be fixed as follows:

1. pass the actual self client state ConnOpen* handlers instead (also, we need to fix the relayer)
2. VerifyClientState of the proxy client wraps the given clientState with MultiV client

This and moving GetTimestampAtHeight function into ClientState will achieve that there is no patch for the core modules.