[net processing] Add Orphanage empty consistency check

When removing the final peer, assert that m_tx_orphanage is empty.

src/net_processing.cpp

@@ -1194,6 +1194,7 @@ void PeerManagerImpl::FinalizeNode(const CNode& node)
         assert(m_outbound_peers_with_protect_from_disconnect == 0);
         assert(m_wtxid_relay_peers == 0);
         assert(m_txrequest.Size() == 0);
+        assert(m_orphanage.Size() == 0);
     }
     } // cs_main
     if (node.fSuccessfullyConnected && misbehavior == 0 &&

src/txorphanage.h

@@ -47,6 +47,13 @@ public:
      * (ie orphans that may have found their final missing parent, and so should be reconsidered for the mempool) */
     void AddChildrenToWorkSet(const CTransaction& tx, std::set<uint256>& orphan_work_set) const EXCLUSIVE_LOCKS_REQUIRED(g_cs_orphans);
 
+    /** Return how many entries exist in the orphange */
+    size_t Size() LOCKS_EXCLUDED(::g_cs_orphans)
+    {
+        LOCK(::g_cs_orphans);
+        return m_orphans.size();
+    }
+
 protected:
     struct OrphanTx {
         CTransactionRef tx;