script: Reduce ScriptThread TLS usage (#38875)

We store a pointer to the ScriptThread singleton for a thread in
thread-local storage. While we don't have yet have profiles pointing to
this TLS access as a hot spot, we can remove a potential performance
footgun without a lot of effort by passing around small pieces of data
that we otherwise need to fetch from the ScriptThread.

Testing: Existing WPT is sufficient
Fixes: part of #37969

---------

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

components/script/dom/domimplementation.rs

@@ -117,6 +117,7 @@ impl DOMImplementationMethods<crate::DomTypeHolder> for DOMImplementation {
             loader,
             Some(self.document.insecure_requests_policy()),
             self.document.has_trustworthy_ancestor_or_current_origin(),
+            self.document.custom_element_reaction_stack(),
             can_gc,
         );
 
@@ -184,6 +185,7 @@ impl DOMImplementationMethods<crate::DomTypeHolder> for DOMImplementation {
             self.document.allow_declarative_shadow_roots(),
             Some(self.document.insecure_requests_policy()),
             self.document.has_trustworthy_ancestor_or_current_origin(),
+            self.document.custom_element_reaction_stack(),
             can_gc,
         );