Add methods for registering both IBC apps and lightclients through the IBCKeeper type

[damiannolan]

Add apis to allow for registering/adding routes of both ibc applications and lightclient modules through the IBCKeeper as one logical point.

I'm not sure this is the ideal approach but came to mind as something I thought was worth discussing - It may be applicable for depinject work as mentioned below, maybe not!

I think there's some other improvements we could probably make to APIs of the core IBCKeeper.
For example right now we require users to create a port router in app.go and bind ibc appmodules there, similarly we retrieve the new light client module router from the clientKeeper and AddRoute for each light client module.

It may be nice to have everything flow through the IBCKeeper, as it essentially is a facade around the set of submodules which make up core ibc.

e.g. IBCKeeper.RegisterClientModule(lightClient) and IBCKeeper.RegisterIBCApplication or something like that, could be useful at some point, maybe these changes may be warranted with depinject work so I think we can hold off on them for now and discuss later. Feel free to drop any thoughts 💭

Originally posted by @damiannolan in #6138 (comment)

Tasks

Beta Give feedback

1. Define new APIs for IBCKeeper if direction is agreed upon
2. Refactor core IBC to use the new APIs instead of accessing the 05-port Router directly
3. Refactor app.go to use new APIs for registering ibc apps and light client modules