gpui: img element object-fit (#9393)

Release Notes:

- Added [object-fit
API](https://developer.mozilla.org/en-US/docs/Web/CSS/object-fit) to the
`img` element. This allows the user to decide how the image is scaled
within the element bounds.
- Fixes corner radius not working as expected on overflowing elements.

crates/gpui/src/platform/blade/shaders.wgsl

@@ -550,7 +550,7 @@ fn fs_poly_sprite(input: PolySpriteVarying) -> @location(0) vec4<f32> {
     }
 
     let sprite = b_poly_sprites[input.sprite_id];
-    let distance = quad_sdf(input.position.xy, sprite.bounds, sprite.corner_radii);
+    let distance = quad_sdf(input.position.xy, sprite.content_mask, sprite.corner_radii);
 
     var color = sample;
     if ((sprite.grayscale & 0xFFu) != 0u) {