Add a stub for rend_service_allow_direct_connection

It always returns 0. It should be replaced with the Single
Onion version from #17178 when both are merged.

src/or/rendservice.c

@@ -3897,3 +3897,11 @@ rend_service_set_connection_addr_port(edge_connection_t *conn,
     return -2;
 }
 
+/* Stub that should be replaced with the #17178 version of the function
+ * when merging. */
+int
+rend_service_allow_direct_connection(const or_options_t *options)
+{
+  (void)options;
+  return 0;
+}

src/or/rendservice.h

@@ -131,5 +131,7 @@ void directory_post_to_hs_dir(rend_service_descriptor_t *renddesc,
                               const char *service_id, int seconds_valid);
 void rend_service_desc_has_uploaded(const rend_data_t *rend_data);
 
+int rend_service_allow_direct_connection(const or_options_t *options);
+
 #endif