[NC-2058] initial scaffolding re block propagation

[smatthewenglish]

PR description

comprises simple method, towards propagation of received blocks to connected peers

inspired by the existing pattern of the codebase, demonstrated here:

   @Override
    public void blockMined(final Block block) {
      // This assumes the block has already been included in the chain
  
      final Optional<UInt256> totalDifficulty = blockchain.getTotalDifficultyByHash(block.getHash());
      if (!totalDifficulty.isPresent()) {
        throw new IllegalStateException(
            "Unable to get total difficulty from blockchain for mined block.");
      }
  
      final NewBlockMessage newBlockMessage = NewBlockMessage.create(block, totalDifficulty.get());
  
      ethPeers
          .availablePeers()
          .forEach(
              peer -> {
                try {
                  peer.send(newBlockMessage);
                } catch (final PeerNotConnected ex) {
                  // Peers may disconnect while traversing the list, this is a normal occurrence.
                }
              });
    }

Fixed Issue(s)

[ajsutton]

LGTM.