Implement event-based IBC handshake relayers

[soareschen]

Summary

In informalsystems/hermes#2925, we implemented the base connection and channel handshake components in relayer-next. However the handshake currently needs to be done manually, and the relayer don't respond to handshake initiated by external users.

In this follow up issue, we will implement event-based connection and channel handshake relayers, so that the relayer would respond to IBC handshake events. To do this, we will implement EventRelayer components that would relay the next handshake step based on a given event. This would work similar to the event-based packet relayers.

Note that an abstraction similar to PacketLock may be needed to ensure that the IBC handshake messages are not sent multiple times.

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