Fix mock module capability claiming in IBC app callbacks

[colin-axner]

Summary

IBC mock module uses capabilities to test redundant packet relays. The capability claiming doesn't account for multiple channels

Problem Definition

When trying to send packets across multiple channels connected to the mock module, the app callbacks will panic

Proposal

Create a helper function with creates the capability name. For example:

func createOnRecvMockCapabilityName() string {
    return fmt.Sprintf("%s%s%s%s", MockRecvCanaryCapabilityName, packet.GetDestPort(), packet.GetDestChannel(), strconv.Itoa(int(packet.GetSequence())))
}

OnAck and OnTimeout should use source port/channel. It might be possible to add dashes to split up the capability name (but I'm not sure what capability name restrictions are)

These helper functions should be called when creating the new capability

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