LibGfx: Unify Rect, Point, and Size

This commit unifies methods and method/param names between the above
classes, as well as adds [[nodiscard]] and ALWAYS_INLINE where
appropriate. It also renamed the various move_by methods to
translate_by, as that more closely matches the transformation
terminology.

Userland/Libraries/LibGfx/Painter.h

@@ -100,7 +100,7 @@ public:
     void clear_clip_rect();
 
     void translate(int dx, int dy) { translate({ dx, dy }); }
-    void translate(const IntPoint& delta) { state().translation.move_by(delta); }
+    void translate(const IntPoint& delta) { state().translation.translate_by(delta); }
 
     Gfx::Bitmap* target() { return m_target.ptr(); }