Verify apps do not need to import simapp

[julienrbrt]

This PR (#13376 ) pointed out that apps still need to import simapp.

We should still verify that there is no other needs to import simapp and provide clear alternatives in the UPGRADING.md

Example:

• https://github.com/cosmos/gaia/blob/main/app/sim_test.go

• https://github.com/CosmWasm/wasmd/blob/main/app/sim_test.go

• refactor: move simapp.App to runtime.AppI #13378

• refactor!: extract simulation helpers out of simapp #13402

[alexanderbez]

Let's ensure we mark this as completed for/before 0.47

cc @marbar3778

[julienrbrt]

AppStateFn is not extracted, as it is very dependent on simapp (at least on simapp/params). I think each app should have theirs, right? Osmosis has theirs, Crypto.com too f.e.

[alexanderbez]

Yup!