message: Add NotifyMasternodeListChanged signal to CClientUIInterface
  And use it instead of BlockTipChanged for mn list changes.
diff: @@ -504,6 +504,7 @@ bool CDeterministicMNManager::ProcessBlock(const CBlock& block, const CBlockInde
  // Don't hold cs while calling signals
  if (diff.HasChanges()) {
  GetMainSignals().NotifyMasternodeListChanged(false, oldList, diff);
  + uiInterface.NotifyMasternodeListChanged();
  }
  const auto& consensusParams = Params().GetConsensus();
  @@ -549,6 +550,7 @@ bool CDeterministicMNManager::UndoBlock(const CBlock& block, const CBlockIndex*
  if (diff.HasChanges()) {
  auto inversedDiff = curList.BuildDiff(prevList);
  GetMainSignals().NotifyMasternodeListChanged(true, curList, inversedDiff);
  + uiInterface.NotifyMasternodeListChanged();
  }
  const auto& consensusParams = Params().GetConsensus();
  