[WIP] deps: upgrade capability to sdk v0.50

[damiannolan]

Description

This PR removes the dependency of ibc-go simapp from the capability module and upgrades it to sdk v0.50

closes: #4055

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[damiannolan]

@tac0turtle I see there's now a HasABCIEndblock interface, is there a similar interface for BeginBlock now or is it inferred somewhere else?

[damiannolan]

I guess this is for legacy? and now core/appmodule is the std with HasBeginBlocker moving forward?

Can't make an interface assertion here yet as arg in the new interface is a regular go ctx

[faddat]

ohhhh this is a WONDEFUL change.

Love how there's no more dependency!

[damiannolan]

I think this PR can be closed and superseded by #4068. After some thought and a few hours of working on this I felt there was more value in refactoring the capability tests to not depend on any simapp at all.

Some of the tests in x/capability have been chopped and changed by many devs pushing code to the sdk over the last couple of years and as a result I think it wasn't clear what the tests were doing. I think few people had a good understanding of what TestInitializeMemStore was doing, mocking a statesync scenario, so I have tried to clean that up and add in-line code comments to make things more clear.