Create new base-app instead of setting it in existing base-app

[nashqueue]

A rollmint light client does not start with a Cosmos-SDK app. In server/start.go, there is a notion of an appCreator which is how a cosmos-sdk app is initially initialized. We'd like to combine SetupBaseAppFromFraudProof described in the fraudproof prototype here with this appCreator.

After this is done, a rollmint light client should be able to spin up a new Cosmos SDK app and initialize its store with Deep Subtrees constructed using merkle inclusion proofs in the FraudProof. After this initialization, the app hash representing the state of the app should match the appHash inside the FraudProof. Also, this store should now contain all the key/value pairs and underlying tree structure necessary to execute the fraudulent state transition contained in the FraudProof.

This issue should also resolve this comment: https://github.com/celestiaorg/cosmos-sdk-rollmint/pull/1/files#r997083032

[Manav-Aggarwal]

#1632 (comment)