Add upgrade timeout rpc to 04-channel protobuf Msg service

[damiannolan]

Summary

It is possible for the channel upgrade process to stall indefinitely on UPGRADE_TRY if the UPGRADE_TRY transaction simply cannot pass on the counterparty; for example, the upgrade feature may not be enabled on the counterparty chain.

In this case, we do not want the initializing chain to be stuck indefinitely in the UPGRADE_INIT step. Thus, the UpgradeInit message will contain a TimeoutHeight and TimeoutTimestamp. The counterparty chain is expected to reject UpgradeTry message if the specified timeout has already elapsed.

A relayer must then submit an ChanUpgradeTimeoutMsg message to the initializing chain which proves that the counterparty is still in its original state. If the proof succeeds, then the initializing chain shall also restore its original channel and cancel the upgrade.

rpc ChannelUpgradeTimeout(MsgChannelUpgradeTimeout) returns (MsgChannelUpgradeTimeoutResponse);

Implement the ChannelUpgradeTimeout functionality as defined in ICS004 - Upgrade Handshake:

• Add ChannelUpgradeTimeout functionality to IBC core Msg server implementation, Implement MsgChannelUpgradeTimeout handler for core IBC msg server #3749
• Add ChanUpgradeTimeout to 04-channel keeper Implement ChanUpgradeTimeout handler for 04-channel keeper #3747
• Implement endpoint.ChanUpgradeTimeout #3748
• Implement WriteUpgradeTimeoutChannel #3750

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[DimitrisJim]

seems like this wasn't closed, closing!