ArgsManager: limit some options to only apply on mainnet when in default section

When specified in bitcoin.conf without using the [regtest] or [test]
section header, or a "regtest." or "test." prefix, the "addnode",
"connect", "port", "bind", "rpcport", "rpcbind", and "wallet" settings
will only be applied when running on mainnet.

src/util.h

@@ -24,6 +24,7 @@
 #include <exception>
 #include <map>
 #include <memory>
+#include <set>
 #include <stdint.h>
 #include <string>
 #include <unordered_set>
@@ -229,9 +230,13 @@ protected:
     std::map<std::string, std::vector<std::string>> m_override_args;
     std::map<std::string, std::vector<std::string>> m_config_args;
     std::string m_network;
+    std::set<std::string> m_network_only_args;
+
     void ReadConfigStream(std::istream& stream);
 
 public:
+    ArgsManager();
+
     /**
      * Select the network in use
      */