Add test ensuring optimstic packet sends are not allowed on ics27

[colin-axner]

Summary

core IBC allows packets to be sent optimistically. That is, a packet can be send on a connection and channel in INIT. ics27 currently disallows this since an active channel needs to be created (requiring ACK handshake step). I think this is the correct decision for v1 of interchain accounts (potentially an optional feature later). We should add a test which verifies this. That what if we modify the ics27 implementation to remove the notion of active channels, we will be forced to revisit this discussion and come to an explicit decision instead of accidentally allowing optimistic sends due to oversight

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