Rename Drawable::boxed to into_element and make containers generic

Multi-element are now generic over any drawable child, which can be converted
into an element.

Co-Authored-By: Nathan Sobo <nathan@zed.dev>
Co-Authored-By: Max Brunsfeld <max@zed.dev>

crates/recent_projects/src/recent_projects.rs

@@ -177,6 +177,6 @@ impl PickerDelegate for RecentProjectsDelegate {
             .flex(1., false)
             .contained()
             .with_style(style.container)
-            .named("match")
+            .into_named_element("match")
     }
 }