message: [net processing] Remove QueuedBlock.fValidatedHeaders
  Since headers-first syncing, we only ever request a block if we've already validated its headers.
  Therefore QueuedBlock.fValidatedHeaders is always set to true. Remove it.
diff: @@ -161,10 +161,12 @@ static constexpr size_t MAX_ADDR_TO_SEND{1000};
  namespace {
  /** Blocks that are in flight, and that are in the queue to be downloaded. */
  struct QueuedBlock {
  + /** Block hash */
  uint256 hash;
  - const CBlockIndex* pindex; //!< Optional.
  - bool fValidatedHeaders; //!< Whether this block has validated headers at the time of request.
  - std::unique_ptr<PartiallyDownloadedBlock> partialBlock; //!< Optional, used for CMPCTBLOCK downloads
  + /** BlockIndex. We must have this since we only request blocks when we've already validated the header. */
  + const CBlockIndex* pindex;
  + /** Optional, used for CMPCTBLOCK downloads */
  + std::unique_ptr<PartiallyDownloadedBlock> partialBlock;
  };
  /**
  @@ -773,8 +775,8 @@ bool PeerManagerImpl::MarkBlockAsReceived(const uint256& hash)
  if (itInFlight != mapBlocksInFlight.end()) {
  CNodeState *state = State(itInFlight->second.first);
  assert(state != nullptr);
  - state->nBlocksInFlightValidHeaders -= itInFlight->second.second->fValidatedHeaders;
  - if (state->nBlocksInFlightValidHeaders == 0 && itInFlight->second.second->fValidatedHeaders) {
  + state->nBlocksInFlightValidHeaders -= 1;
  + if (state->nBlocksInFlightValidHeaders == 0) {
  // Last validated block on the queue was received.
  nPeersWithValidatedDownloads--;
  }
  @@ -812,9 +814,9 @@ bool PeerManagerImpl::MarkBlockAsInFlight(NodeId nodeid, const CBlockIndex* pind
  MarkBlockAsReceived(hash);
  std::list<QueuedBlock>::iterator it = state->vBlocksInFlight.insert(state->vBlocksInFlight.end(),
  - {hash, pindex, pindex != nullptr, std::unique_ptr<PartiallyDownloadedBlock>(pit ? new PartiallyDownloadedBlock(&m_mempool) : nullptr)});
  + {hash, pindex, std::unique_ptr<PartiallyDownloadedBlock>(pit ? new PartiallyDownloadedBlock(&m_mempool) : nullptr)});
  state->nBlocksInFlight++;
  - state->nBlocksInFlightValidHeaders += it->fValidatedHeaders;
  + state->nBlocksInFlightValidHeaders += 1;
  if (state->nBlocksInFlight == 1) {
  // We're starting a block download (batch) from this peer.
  state->m_downloading_since = GetTime<std::chrono::microseconds>();
  