util: Add 'render' debug topic

Meant for MetaRenderer and everything related that deals with turning
composited frames, or client buffers, into mode set updates. This is
slightly related to the debug topic 'kms' is meant for the KMS details.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1854>

src/core/util.c

@@ -71,6 +71,7 @@ static const GDebugKey meta_debug_keys[] = {
   { "screen-cast", META_DEBUG_SCREEN_CAST },
   { "remote-desktop", META_DEBUG_REMOTE_DESKTOP },
   { "backend", META_DEBUG_BACKEND },
+  { "render", META_DEBUG_RENDER },
 };
 
 #ifdef WITH_VERBOSE_MODE
@@ -329,6 +330,8 @@ topic_name (MetaDebugTopic topic)
       return "REMOTE_DESKTOP";
     case META_DEBUG_BACKEND:
       return "BACKEND";
+    case META_DEBUG_RENDER:
+      return "RENDER";
     case META_DEBUG_VERBOSE:
       return "VERBOSE";
     }