[LAOS] Add function to retrieve the rejected and accepted transaction hashes

[appetrosyan]

As per request, the mechanisms for retrieving the hashes of accepted and rejected transactions are not obvious.

As a possible solution, Igor suggests adding two functions into jp.co.soramitsu.iroha2.Extensions

fun VersionedRejectedTransaction.V1.hash(): ByteArray {
    return this.rejectedTransaction
        .payload
        .let { TransactionPayload.encode(it) }
        .hash()
}

fun VersionedValidTransaction.V1.hash(): ByteArray {
    return this.validTransaction
        .payload
        .let { TransactionPayload.encode(it) }
        .hash()
}

[Mingela]

If the scope of the issue is just this please just create a PR right away instead. Don't treat this rude, that'd be just much quicker than waiting for someone else to pick this up. We're always happy to have more contributors.

[appetrosyan]

I suppose we have different processes. Happy to create the PR