Style: Apply clang-tidy fixes

• `modernize-use-default-member-init` and `readability-redundant-member-init`
• Minor adjustments to `.clang-tidy` to improve syntax & remove redundancies

scene/gui/text_edit.h

@@ -139,7 +139,7 @@ private:
 			Variant metadata;
 			bool clickable = false;
 
-			Ref<Texture2D> icon = Ref<Texture2D>();
+			Ref<Texture2D> icon;
 			String text = "";
 			Color color = Color(1, 1, 1);
 		};