Merge bitcoin/bitcoin#21775: p2p: Limit m_block_inv_mutex

fac96d0 p2p: Limit m_block_inv_mutex (MarcoFalke)

Pull request description:

  Keeping the lock longer than needed is confusing to reviewers and thread analysis. For example, keeping the lock while appending tx-invs, which requires the mempool lock, will tell thread analysis tools an incorrect lock order of `(1) m_block_inv_mutex, (2) pool.cs`.

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Tree-SHA512: fcfac0f1f8b16df7522513abf716b2eed3d2fc9153f231c8cb61f451e342f29c984a5c872deca6bab3e601e5d651874cc229146c9370e46811b4520747a21f2b

src/net_processing.cpp

@@ -4449,8 +4449,9 @@ bool PeerManagerImpl::SendMessages(CNode* pto)
                 }
             }
             peer->m_blocks_for_inv_relay.clear();
+        }
 
-            if (pto->m_tx_relay != nullptr) {
+        if (pto->m_tx_relay != nullptr) {
                 LOCK(pto->m_tx_relay->cs_tx_inventory);
                 // Check whether periodic sends should happen
                 bool fSendTrickle = pto->HasPermission(PF_NOBAN);
@@ -4578,7 +4579,6 @@ bool PeerManagerImpl::SendMessages(CNode* pto)
                         }
                     }
                 }
-            }
         }
         if (!vInv.empty())
             m_connman.PushMessage(pto, msgMaker.Make(NetMsgType::INV, vInv));