migrate error packages

[tac0turtle]

Summary

Cosmos SDK has spun out the errors package into its own go.mod in light of the recent conversation on reducing dependency on the sdk, ibc-go should be migrated to cosmossdk.io/errors to take advantage of this.

We did not move the default error types over cause the idea is that users/app devs will create their own with their custom codespace.

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[damiannolan]

We did not move the default error types over cause the idea is that users/app devs will create their own with their custom codespace.

Should ibc-go not be using the default types from the sdk root codespace then, such as ErrInvalidCoins, ErrInvalidAddress etc?