rpc: Register calls where they are defined

Split out methods to every module, apart from 'help' and 'stop' which
are implemented in rpcserver.cpp itself.

- This makes it easier to add or remove RPC commands - no longer everything that includes
    rpcserver.h has to be rebuilt when there's a change there.
- Cleans up `rpc/server.h` by getting rid of the huge cluttered list of function definitions.
- Removes most of the bitcoin-specific code from rpcserver.cpp and .h.

Continues #7307 for the non-wallet.

src/rpc/net.cpp

@@ -626,3 +626,25 @@ UniValue clearbanned(const UniValue& params, bool fHelp)
 
     return NullUniValue;
 }
+
+static const CRPCCommand commands[] =
+{ //  category              name                      actor (function)         okSafeMode
+  //  --------------------- ------------------------  -----------------------  ----------
+    { "network",            "getconnectioncount",     &getconnectioncount,     true  },
+    { "network",            "ping",                   &ping,                   true  },
+    { "network",            "getpeerinfo",            &getpeerinfo,            true  },
+    { "network",            "addnode",                &addnode,                true  },
+    { "network",            "disconnectnode",         &disconnectnode,         true  },
+    { "network",            "getaddednodeinfo",       &getaddednodeinfo,       true  },
+    { "network",            "getnettotals",           &getnettotals,           true  },
+    { "network",            "getnetworkinfo",         &getnetworkinfo,         true  },
+    { "network",            "setban",                 &setban,                 true  },
+    { "network",            "listbanned",             &listbanned,             true  },
+    { "network",            "clearbanned",            &clearbanned,            true  },
+};
+
+void RegisterNetRPCCommands(CRPCTable &tableRPC)
+{
+    for (unsigned int vcidx = 0; vcidx < ARRAYLEN(commands); vcidx++)
+        tableRPC.appendCommand(commands[vcidx].name, &commands[vcidx]);
+}