Propagate ibc authority to 04-channel to be used within upgrade cancellation

[damiannolan]

Summary

The authority of the ibc module is required in order to do some privileged action when performing a cancellation of an upgrade.

We should determine how we want to access the authority from the 04-channel submodule, and other submodule if required in future. The authority currently exists as a field on the IBCKeeper and is exposed through the GetAuthority method. However, submodule keepers composed within the IBCKeeper cannot reach this.

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[damiannolan]

Adding needs-discussion label so we can align on the approach here prior to completing the issue

[damiannolan]

After discussion, let's check msg.Signer against k.GetAuthority in the msg server handler and pass a bool to 04-channel in order to infer if it is an authorized upgrader or not. This decides whether or not proof verification is carried out