add GetVersions() as an interface method for exported.ConnecionI

[charleenfei]

currently, we need to get an instance of ConnectionEnd in order to use GetVersions()

should we add GetVersions() as an interface method to exported.ConnectionI? cc. @colin-axner

Originally posted by @damiannolan in #3774 (comment)

[damiannolan]

Awesome, thanks for opening this issue @charleenfei. We can update the code from where I made the comment on the 04-channel-upgrades branch once this is changed :)

We can make this to main and then resync the feat branch whenever 👍

[crodriguezvega]

This is the issue that we had in the past to remove GetVersions from the interface.

[colin-axner]

I think we can just modify channelKeeper.GetConnection() to return the concrete connection type? I see connection types is imported by channel types, so I'm not sure what import cycle is being avoided using exported.

The usage of interface to avoid import cycles is quite dated. We didn't think it through too much at the time for the sake of delivering IBC faster, so I think it's worth trying to remove some of these unnecessary interfaces

[crodriguezvega]

If that's ok, I will close this for now, since we decided (and already implemented) to use the connection keeper to get the connection (which returns the concrete type), so this should not be needed anymore.