Add ability for create sequencer/update transaction for reward distribution

[omritoptix]

the idea is that the sequencer has the ability to prove that he is indeed the owner of the consensus key, and couple a reward address to it, as the rewards are currently expecting an sdk address, and the sdk address is being fetched based on the sequencer consensus address.

// calculate and pay proposer reward
    proposer, found := k.seqKeeper.GetSequencerByConsAddr(ctx, blockProposer)
    if !found {
        logger.Error("failed to find the validator for this block. reward not allocated")
    } else {