net: make the list of known message types a compile time constant

Turn the `std::vector` to `std::array` because it is cheaper and
allows us to have the number of the messages as a compile time
constant: `ALL_NET_MESSAGE_TYPES.size()` which can be used in
future code to build other `std::array`s with that size.

src/net.cpp

@@ -3701,8 +3701,9 @@ CNode::CNode(NodeId idIn,
 {
     if (inbound_onion) assert(conn_type_in == ConnectionType::INBOUND);
 
-    for (const std::string &msg : getAllNetMessageTypes())
+    for (const auto& msg : ALL_NET_MESSAGE_TYPES) {
         mapRecvBytesPerMsgType[msg] = 0;
+    }
     mapRecvBytesPerMsgType[NET_MESSAGE_TYPE_OTHER] = 0;
 
     if (fLogIPs) {