Add upgrade cancellation rpc to 04-channel protobuf Msg service

[damiannolan]

Summary

During the upgrade handshake a chain may cancel the upgrade by writing an error receipt into the error path and restoring the original channel to OPEN. The counterparty must then restore its channel to OPEN as well. A relayer can facilitate this by sending ChanUpgradeCancelMsg to the handler:

rpc ChannelUpgradeCancel(MsgChannelUpgradeCancel) returns (MsgChannelUpgradeCancelResponse);

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

• Add ChannelUpgradeCancel functionality to IBC core Msg server implementation Implement MsgChannelUpgradeCancel handler for core IBC msg server #3754
• Add ChanUpgradeCancel to 04-channel keeper Implement ChanUpgradeCancel handler for 04-channel keeper #3753
• Implement WriteUpgradeCancelChannel #3752
• Implement endpoint.ChanUpgradeCancel #3755

---

For Admin Use

• Not duplicate issue
• Appropriate labels applied
• Appropriate contributors tagged/assigned