Just pass a TxId to AddInventoryKnown, rename to AddKnownTx

Summary:
```
Since it's only used for transactions, there's no need to pass in an inv
type.
```

Backport of core [[bitcoin/bitcoin#18044 | PR18044]].

Since thie PR is Segwit related, there is not much left.
Full commits:
 - bitcoin/bitcoin@60f0acd
 - bitcoin/bitcoin@dd78d1d
Only the CInv equality operator in messages.py is relevant:
 - bitcoin/bitcoin@9a5392f

Test Plan:
  ninja all check-all

Reviewers: #bitcoin_abc, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D8501

Author: sdaftuar

src/net.h

@@ -1018,10 +1018,10 @@ class CNode {
         }
     }
 
-    void AddInventoryKnown(const CInv &inv) {
+    void AddKnownTx(const TxId &txid) {
         if (m_tx_relay != nullptr) {
             LOCK(m_tx_relay->cs_tx_inventory);
-            m_tx_relay->filterInventoryKnown.insert(inv.hash);
+            m_tx_relay->filterInventoryKnown.insert(txid);
         }
     }
 

src/net_processing.cpp

@@ -2897,18 +2897,18 @@ bool ProcessMessage(const Config &config, CNode &pfrom,
                              pfrom.GetId());
                 }
             } else {
-                pfrom.AddInventoryKnown(inv);
+                const TxId txid(inv.hash);
+                pfrom.AddKnownTx(txid);
                 if (fBlocksOnly) {
                     LogPrint(BCLog::NET,
                              "transaction (%s) inv sent in violation of "
                              "protocol, disconnecting peer=%d\n",
-                             inv.hash.ToString(), pfrom.GetId());
+                             txid.ToString(), pfrom.GetId());
                     pfrom.fDisconnect = true;
                     return true;
                 } else if (!fAlreadyHave && !fImporting && !fReindex &&
                            !::ChainstateActive().IsInitialBlockDownload()) {
-                    RequestTx(State(pfrom.GetId()), TxId(inv.hash),
-                              current_time);
+                    RequestTx(State(pfrom.GetId()), txid, current_time);
                 }
             }
         }
@@ -3175,9 +3175,7 @@ bool ProcessMessage(const Config &config, CNode &pfrom,
         vRecv >> ptx;
         const CTransaction &tx = *ptx;
         const TxId &txid = tx.GetId();
-
-        CInv inv(MSG_TX, txid);
-        pfrom.AddInventoryKnown(inv);
+        pfrom.AddKnownTx(txid);
 
         LOCK2(cs_main, g_cs_orphans);
 
@@ -3188,7 +3186,7 @@ bool ProcessMessage(const Config &config, CNode &pfrom,
         nodestate->m_tx_download.m_tx_in_flight.erase(txid);
         EraseTxRequest(txid);
 
-        if (!AlreadyHave(inv) &&
+        if (!AlreadyHave(CInv(MSG_TX, txid)) &&
             AcceptToMemoryPool(config, g_mempool, state, ptx,
                                false /* bypass_limits */,
                                Amount::zero() /* nAbsurdFee */)) {
@@ -3231,9 +3229,8 @@ bool ProcessMessage(const Config &config, CNode &pfrom,
                 for (const CTxIn &txin : tx.vin) {
                     // FIXME: MSG_TX should use a TxHash, not a TxId.
                     const TxId _txid = txin.prevout.GetTxId();
-                    CInv _inv(MSG_TX, _txid);
-                    pfrom.AddInventoryKnown(_inv);
-                    if (!AlreadyHave(_inv)) {
+                    pfrom.AddKnownTx(_txid);
+                    if (!AlreadyHave(CInv(MSG_TX, _txid))) {
                         RequestTx(State(pfrom.GetId()), _txid, current_time);
                     }
                 }

test/functional/test_framework/messages.py

@@ -266,6 +266,10 @@ def __repr__(self):
         return "CInv(type={} hash={:064x})".format(
             self.typemap[self.type], self.hash)
 
+    def __eq__(self, other):
+        return isinstance(
+            other, CInv) and self.hash == other.hash and self.type == other.type
+
 
 class CBlockLocator:
     __slots__ = ("nVersion", "vHave")