gpui: Add SVG rendering to img element and generic asset cache (#9931)

This is a follow up to #9436 . It has a cleaner API and generalized the
image_cache to be a generic asset cache, that all GPUI elements can make
use off. The changes have been discussed with @mikayla-maki on Discord.

---------

Co-authored-by: Mikayla <mikayla@zed.dev>

crates/gpui/src/assets.rs

@@ -34,6 +34,11 @@ impl AssetSource for () {
 #[derive(Copy, Clone, Debug, Eq, PartialEq, Ord, PartialOrd, Hash)]
 pub struct ImageId(usize);
 
+#[derive(PartialEq, Eq, Hash, Clone)]
+pub(crate) struct RenderImageParams {
+    pub(crate) image_id: ImageId,
+}
+
 /// A cached and processed image.
 pub struct ImageData {
     /// The ID associated with this image