Rename "Singleton" to "Global Variable" in the AutoLoad editor

The name "Singleton" was misleading because Godot does not actually
enforce a singleton pattern for autoloads. They can be instanced
multiple times.

"Global Variable" makes it more obvious that all the checkbox does
is expose the AutoLoad with a global variable for easy access.

(cherry picked from commit 1e53bac8b48702bc8d80142094b956f20edee82c)

editor/editor_autoload_settings.cpp

@@ -871,15 +871,16 @@ EditorAutoloadSettings::EditorAutoloadSettings() {
 
 	tree->set_column_title(0, TTR("Name"));
 	tree->set_column_expand(0, true);
-	tree->set_column_min_width(0, 100);
+	tree->set_column_min_width(0, 100 * EDSCALE);
 
 	tree->set_column_title(1, TTR("Path"));
 	tree->set_column_expand(1, true);
-	tree->set_column_min_width(1, 100);
+	tree->set_column_min_width(1, 100 * EDSCALE);
 
-	tree->set_column_title(2, TTR("Singleton"));
+	tree->set_column_title(2, TTR("Global Variable"));
 	tree->set_column_expand(2, false);
-	tree->set_column_min_width(2, 80 * EDSCALE);
+	// Reserve enough space for translations of "Global Variable" which may be longer.
+	tree->set_column_min_width(2, 150 * EDSCALE);
 
 	tree->set_column_expand(3, false);
 	tree->set_column_min_width(3, 120 * EDSCALE);