private static Address calculateRoundSpecificValidator(
      final Address baseProposer,
      final Collection<Address> validatorsForRound,
      final int indexOffset) {
    final List<Address> currentValidatorList = new ArrayList<>(validatorsForRound);
    final int prevProposerIndex = currentValidatorList.indexOf(baseProposer);
    final int roundValidatorIndex = (prevProposerIndex + indexOffset) % currentValidatorList.size();
    return currentValidatorList.get(roundValidatorIndex);
  }
Given Round 0 of the given height should start from given proposer (baseProposer) - determine
which validator should be used given the indexOffset.
consensus/common/src/main/java/org/hyperledger/besu/consensus/common/bft/blockcreation/BftProposerSelector.java