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/node/node.rs

@@ -1997,6 +1997,7 @@ impl Node {
     pub(crate) fn set_implemented_pseudo_element(&self, pseudo_element: PseudoElement) {
         // Implemented pseudo element should exist only in the UA shadow DOM.
         debug_assert!(self.is_in_ua_widget());
+        debug_assert!(pseudo_element.is_element_backed());
         self.ensure_rare_data().implemented_pseudo_element = Some(pseudo_element);
     }