Merge #16452: refactor: use RelayTransaction in BroadcastTransaction utility

9bc8b28c1d refactor : use RelayTransaction in BroadcastTransaction utility (Antoine Riard)

Pull request description:

  Implementing suggestion in https://github.com/bitcoin/bitcoin/pull/15713#discussion_r306571420.

  Seems a reason of these node utilities is to glue with already there functions, so we should reuse them.

ACKs for top commit:
  MarcoFalke:
    ACK 9bc8b28c1d
  promag:
    ACK 9bc8b28c1d, verified there are no more `PushInventory(CInv(MSG_TX, ...`, nice refactor, 👍 @amitiuttarwar.
  jnewbery:
    ACK 9bc8b28c1d
  jonatack:
    ACK 9bc8b28c1d, second @jnewbery's suggestions, my guess is they could be added without risking delaying this PR.

Tree-SHA512: 841c65d5f0d9ead5380814bb2260d7ebf03f2a9bfa58a1025785d353bdb42f9122cc257993e6a7bd2bd3f2c74db19c5978cc14be0d83258124ca22e33d6d0164

src/interfaces/chain.cpp

@@ -9,6 +9,7 @@
 #include <interfaces/handler.h>
 #include <interfaces/wallet.h>
 #include <net.h>
+#include <net_processing.h>
 #include <node/coin.h>
 #include <policy/fees.h>
 #include <policy/policy.h>
@@ -292,8 +293,7 @@ public:
     }
     void relayTransaction(const uint256& txid) override
     {
-        CInv inv(MSG_TX, txid);
-        g_connman->ForEachNode([&inv](CNode* node) { node->PushInventory(inv); });
+        RelayTransaction(txid, *g_connman);
     }
     void getTransactionAncestry(const uint256& txid, size_t& ancestors, size_t& descendants) override
     {