MM-13015 Add safety valve setting to disable post metadata (#9877)

* MM-13015 Add safety valve setting to disable post metadata

* Remove setting from client config since it's no longer needed

app/post_metadata.go

@@ -52,6 +52,10 @@ func (a *App) PreparePostForClient(originalPost *model.Post) *model.Post {
 	// Proxy image links before constructing metadata so that requests go through the proxy
 	post = a.PostWithProxyAddedToImageURLs(post)
 
+	if *a.Config().ExperimentalSettings.DisablePostMetadata {
+		return post
+	}
+
 	post.Metadata = &model.PostMetadata{}
 
 	// Emojis and reaction counts