Reduce the usage of ibc-rs types

[srdtrk]

Summary

We often use ibc-rs types to decode/encode requests/responses from Cosmos SDK in the operator and relayer. We should instead only use ibc-proto whenever possible to reduce the number of dependencies.

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[gjermundgaraba]

Is this still something we should be doing? Or do we need a more holistic approach that we have more control over ourselves here?