Merge bitcoin/bitcoin#28592: p2p: Increase tx relay rate

b81f370 p2p: Increase tx relay rate (Anthony Towns)

Pull request description:

  In the presence of smaller transactions on the network, blocks can sustain a higher relay rate than 7tx/second. In this event, the per-peer inventory queues can grow too large.

  This commit bumps the rate up to 14 tx/s (for inbound peers), increasing the safety margin by a factor of 2.

  Outbound peers continue to receive relayed transactions at 2.5x the rate of inbound peers, for a rate of 35tx/second.

ACKs for top commit:
  sipa:
    ACK b81f370
  achow101:
    ACK b81f370
  darosior:
    utACK b81f370.
  glozow:
    utACK b81f370

Tree-SHA512: 854ea0824d5f4c629f1dceb9ee61cc9226c8f0d4d26664737e68db917f65341d4800362ab55ed32673db920b2b59aa116b4cb9ee063367b2e43c94a904b41c08

Author: fanquake

src/net_processing.cpp

@@ -167,7 +167,7 @@ static constexpr auto INBOUND_INVENTORY_BROADCAST_INTERVAL{5s};
 static constexpr auto OUTBOUND_INVENTORY_BROADCAST_INTERVAL{2s};
 /** Maximum rate of inventory items to send per second.
  *  Limits the impact of low-fee transaction floods. */
-static constexpr unsigned int INVENTORY_BROADCAST_PER_SECOND = 7;
+static constexpr unsigned int INVENTORY_BROADCAST_PER_SECOND{14};
 /** Target number of tx inventory items to send per transmission. */
 static constexpr unsigned int INVENTORY_BROADCAST_TARGET = INVENTORY_BROADCAST_PER_SECOND * count_seconds(INBOUND_INVENTORY_BROADCAST_INTERVAL);
 /** Maximum number of inventory items to send per transmission. */