fix: return request key alongside smt proof

[juan518munoz]

When the client calls get_account_proof to request storage maps by passing specific keys, the node retrieves the requested values by querying the Smt forest with a hash of each requested key. Finally, the node returns the requested proofs with the hashed keys, when in reality the original requested keys are needed to construct the StorageMapWitness.

Original discussion

[Mirko-von-Leipzig]

But don't you already have the keys since you requested them?

[drahnr]

As @Mirko-von-Leipzig said, you do have the keys, and you can apply the hash function to map the responded proofs back using a hashmap? I do understand it'd be more convenient to get the keys returned. @bobbinth was pretty concerned re request/response sizes (there is one more issue to compress these proofs even further), so I am not sure we want to throw in these bytes.

[juan518munoz]

As discussed offline with @igamigo and @TomasArrachea, it makes sense to not return the keys as one can assume the user knows them beforehand (otherwise it'd be impossible to request proof of them).

Closing this PR.