rpc: fix successful broadcast count in submitpackage error msg

If a `submitpackage` RPC call errors due to any of the individual tx
broadcasts failing, the returned error message is supposed to contain
the number of successful broadcasts so far. Right now this is wrongly
always shown as zero. Fix this by adding the missing counting.
(Note though that the error should be really rare, as all txs have
already been submitted succesfully to the mempool.)

Author: theStack

src/rpc/mempool.cpp

@@ -839,15 +839,16 @@ static RPCHelpMan submitpackage()
                     NONFATAL_UNREACHABLE();
                 }
             }
+            size_t num_broadcast{0};
             for (const auto& tx : txns) {
-                size_t num_submitted{0};
                 std::string err_string;
-                const auto err = BroadcastTransaction(node, tx, err_string, 0, true, true);
+                const auto err = BroadcastTransaction(node, tx, err_string, /*max_tx_fee=*/0, /*relay=*/true, /*wait_callback=*/true);
                 if (err != TransactionError::OK) {
                     throw JSONRPCTransactionError(err,
                         strprintf("transaction broadcast failed: %s (all transactions were submitted, %d transactions were broadcast successfully)",
-                            err_string, num_submitted));
+                            err_string, num_broadcast));
                 }
+                num_broadcast++;
             }
             UniValue rpc_result{UniValue::VOBJ};
             UniValue tx_result_map{UniValue::VOBJ};