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/mac/shaders.metal

@@ -372,7 +372,7 @@ fragment float4 polychrome_sprite_fragment(
   float4 sample =
       atlas_texture.sample(atlas_texture_sampler, input.tile_position);
   float distance =
-      quad_sdf(input.position.xy, sprite.bounds, sprite.corner_radii);
+      quad_sdf(input.position.xy, sprite.content_mask.bounds, sprite.corner_radii);
 
   float4 color = sample;
   if (sprite.grayscale) {