Split Connect/Close callbacks in IbcContract interface into 2 variants.

[ethanfrey]

Question: do we want to do so?

We use an argument to construct IbcConnectInit or IbcConnectTry from an IbcConnectOpen callback. We could split this into 2 methods, or we could use a IbcConnectOpenMsg as an argument (which captures the 2 variants).

It could definitely be cleaner than mine, which I did to make minimal changes. I'd like feedback from @alpe to do this.

[alpe]

The new types are cleaner in wasmd so I like them. Though they push the complexity of handling more cases upstream.

[ethanfrey]

The work in cosmwasm is nice, such that you can call a helper msg.channel() to get the information common to both variants and not care about which one (as now), or actually switch on variant (if you care).

It is quite nice actually, from a fair bit of back and forth. At least it provides the contracts the possibility of handling the different events differently