Upgrade Stylo to 2026-04-01 (#43878)

This continues  #43045

Changelog:
- Upstream:
74ddab4091...6de1071549
- Servo fixups:
9f2f4f3f1b...6cfce6f329

Stylo tracking issue: https://github.com/servo/stylo/issues/347

Summary of improvements:
 - Adding support for the CSS-wide `revert-rule` keyword
- `::details-content` becomes element-backed, thus accepting nested
pseudo-elements like `::details-content::before`.
- Custom properties can now be registered using dashed idents in their
syntax
 - Various `attr()` improvements

Testing: Various WPT improvements

---------

Signed-off-by: Oriol Brufau <obrufau@igalia.com>

components/script/dom/css/cssrule.rs

@@ -139,6 +139,8 @@ impl CSSRule {
                 s,
                 can_gc,
             )),
+            StyleCssRule::AppearanceBase(_) => unimplemented!(), // TODO
+            StyleCssRule::ViewTransition(_) => unimplemented!(), // TODO
         }
     }
 
@@ -233,6 +235,8 @@ impl CSSRule {
                     rule.update_rule(s.clone(), guard);
                 }
             },
+            StyleCssRule::AppearanceBase(_) => unimplemented!(), // TODO
+            StyleCssRule::ViewTransition(_) => unimplemented!(), // TODO
         }
     }
 }