Refactor texture image filtering

- Support only `Linear` or `Nearest`
- Simplify `Layer` groups
- Move `FilterMethod` to `Image` and `image::Viewer`

graphics/src/primitive.rs

@@ -68,6 +68,8 @@ pub enum Primitive<T> {
     Image {
         /// The handle of the image
         handle: image::Handle,
+        /// The filter method of the image
+        filter_method: image::FilterMethod,
         /// The bounds of the image
         bounds: Rectangle,
     },

graphics/src/renderer.rs

@@ -215,8 +215,17 @@ where
         self.backend().dimensions(handle)
     }
 
-    fn draw(&mut self, handle: image::Handle, bounds: Rectangle) {
-        self.primitives.push(Primitive::Image { handle, bounds });
+    fn draw(
+        &mut self,
+        handle: image::Handle,
+        filter_method: image::FilterMethod,
+        bounds: Rectangle,
+    ) {
+        self.primitives.push(Primitive::Image {
+            handle,
+            filter_method,
+            bounds,
+        });
     }
 }