refactor: move GetServicesNames from rpc/util.{h,cpp} to rpc/net.cpp

as it is only called from that compilation unit.

This avoids needlessly compiling GetServicesNames() in the 35 other files that
include rpc/util.h.

src/rpc/net.cpp

@@ -15,6 +15,7 @@
 #include <netbase.h>
 #include <node/context.h>
 #include <policy/settings.h>
+#include <protocol.h>
 #include <rpc/blockchain.h>
 #include <rpc/protocol.h>
 #include <rpc/server_util.h>
@@ -91,6 +92,18 @@ static RPCHelpMan ping()
     };
 }
 
+/** Returns, given services flags, a list of humanly readable (known) network services */
+static UniValue GetServicesNames(ServiceFlags services)
+{
+    UniValue servicesNames(UniValue::VARR);
+
+    for (const auto& flag : serviceFlagsToStr(services)) {
+        servicesNames.push_back(flag);
+    }
+
+    return servicesNames;
+}
+
 static RPCHelpMan getpeerinfo()
 {
     return RPCHelpMan{