Move tracing to IAVL tree substore for Fraud Proof implementation

[Manav-Aggarwal]

We'd like to modify the witness data in the FraudProof struct to use witness data generated by the IAVL tree substore in rollkit/iavl#19

This enables us to use the IAVL tree substore entirely for tracing and during verification of fraud proofs, we can load this witness data into a Deep Subtree so that it performs the same underlying tree operations for a fraudulent transaction.

Relevant changes to accommodate this design change should be made in ABCI methods GenerateFraudProof and VerifyFraudProof (and methods used by them).

We should also delete any new tracing related things we added to tracekv and rootmulti store on the cosmos-sdk level since all the tracing happens in the underlying IAVL tree substore now.