layout: Add support for object-fit and object-position (#33479)

This also makes a couple small improvements:
 - Rename `IntrinsicSizes` to `NaturalSizes` which reflects more
   modern spec language.
 - Move the conversion of Stylo's `ImageRendering` to WebRender's
   version to a `ToWebRender` trait implementation.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>
Co-authored-by: Oriol Brufau <obrufau@igalia.com>

components/layout_2020/flexbox/layout.rs

@@ -1772,6 +1772,7 @@ impl FlexItem<'_> {
                 let cross_size = flex_axis.vec2_to_flex_relative(size).cross;
                 let fragments = replaced.contents.make_fragments(
                     &replaced.style,
+                    containing_block,
                     size.to_physical_size(container_writing_mode),
                 );