[k2] add missed doc comment for builtins stubs (#1488)

Author: astrophysik

builtin-functions/kphp-light/stdlib/server-functions.txt

@@ -102,8 +102,9 @@ function memory_get_static_usage() ::: int;
 /** @kphp-extern-func-info stub */
 function kphp_extended_instance_cache_metrics_init(callable(string $key):string $normalization_function) ::: void;
 
-
+/** @kphp-extern-func-info stub */
 function register_kphp_on_warning_callback(callable(string $warning_message, string[] $stacktrace):void $stacktrace) ::: void;
+/** @kphp-extern-func-info stub */
 function register_kphp_on_oom_callback(callable():void $callback) ::: bool;
 
 /** @kphp-extern-func-info stub */

runtime-light/stdlib/system/system-functions.h

@@ -79,7 +79,7 @@ auto exec(std::string_view cmd, const output_handler_type& output_handler = {})
 
 template<typename F>
 bool f$register_kphp_on_oom_callback(F&& /*callback*/) {
-  kphp::log::error("call to unsupported function");
+  kphp::log::warning("called stub register_kphp_on_oom_callback");
 }
 
 template<typename F>
@@ -237,12 +237,10 @@ inline Optional<string> f$exec(const string& cmd) noexcept {
 }
 
 inline string f$get_engine_version() noexcept {
-  kphp::log::warning("called stub get_engine_version");
   return {};
 }
 
 inline string f$get_kphp_cluster_name() noexcept {
-  kphp::log::warning("called stub get_kphp_cluster_name");
   return string{"adm512"};
 }