Add handling of channel upgrades to ADR 008

[colin-axner]

Summary

Once ibc-go supports upgrading channels, logic on how this should be handled/supported by ADR 008 implementations should be added to the ADR itself.

see comment

---

For Admin Use

• Not duplicate issue
• Appropriate labels applied
• Appropriate contributors tagged/assigned

[crodriguezvega]

I think we can close this issue, because when it was created the ADR had an IBCActor interface with channel handshake callbacks, but that interface was later removed and the ContractKeeper interface that we have now only has entry points for the packet callbacks. I will close it now, we can re-open if I am wrong in my reasoning.