script: Check same-origin-domain when evaluating javscript: URLs. (#41969)

These changes introduce a new OriginSnapshot type, which is an immutable
version of MutableOrigin (ie. an origin that includes an optional domain
modifier). This is now propagated as part of LoadData's origin, allowing
us to perform the same-origin-domain check for javascript: URLs as
needed.

Testing: Newly-passing tests.

Signed-off-by: Josh Matthews <josh@joshmatthews.net>

components/script/dom/html/htmlformelement.rs

@@ -872,7 +872,7 @@ impl HTMLFormElement {
         // Step 21
         let target_window = target_document.window();
         let mut load_data = LoadData::new(
-            LoadOrigin::Script(doc.origin().immutable().clone()),
+            LoadOrigin::Script(doc.origin().snapshot()),
             action_components,
             None,
             target_window.as_global_scope().get_referrer(),