p2p: clear txreconciliation state for non-wtxid peers

We optimistically pre-register a peer for txreconciliations
upon sending txreconciliation support announcement.
But if, at VERACK, we realize that the peer never sent
WTXIDRELAY message, we should unregister the peer
from txreconciliations, because txreconciliations rely on wtxids.

src/net_processing.cpp

@@ -3414,6 +3414,16 @@ void PeerManagerImpl::ProcessMessage(CNode& pfrom, const std::string& msg_type,
             // they may wish to request compact blocks from us
             m_connman.PushMessage(&pfrom, msgMaker.Make(NetMsgType::SENDCMPCT, /*high_bandwidth=*/false, /*version=*/CMPCTBLOCKS_VERSION));
         }
+
+        if (m_txreconciliation) {
+            if (!peer->m_wtxid_relay || !m_txreconciliation->IsPeerRegistered(pfrom.GetId())) {
+                // We could have optimistically pre-registered/registered the peer. In that case,
+                // we should forget about the reconciliation state here if this wasn't followed
+                // by WTXIDRELAY (since WTXIDRELAY can't be announced later).
+                m_txreconciliation->ForgetPeer(pfrom.GetId());
+            }
+        }
+
         pfrom.fSuccessfullyConnected = true;
         return;
     }