No tracing of nop traceable fields (#29926)

* Add `no_trace` option to JSTraceable derive

* NoTrace wrapper

* Port some types to no_trace schematics

* Fixing my unsafe mistakes (not tracing traceables)

* Add docs & safety guards for no_trace

Safety guards (trait shenanigans) guarantees safety usage of `no_trace`

* Port canvas_traits to no_trace

* Port servo_media to no_trace

* Port net_traits to no_trace

* Port style to no_trace

* Port webgpu to no_trace

* Port script_traits to no_trace

* Port canvas_traits, devtools_traits, embedder_traits, profile_traits to no_trace

* unrooted_must_root lint in seperate file

* Add trace_in_no_trace_lint as script_plugin

* Composable types in must_not_have_traceable

* Introduced HashMapTracedValues wrapper

* `HashMap<NoTrace<K>,V>`->`HashMapTracedValues<K,V>`

* Port rest of servo's types to no_trace

* Port html5ever, euclid, mime and http to no_trace

* Port remaining externals to no_trace

* Port webxr and Arc<Mutex<_>>

* Fix spelling in notrace doc

components/script/document_loader.rs

@@ -17,11 +17,11 @@ use servo_url::ServoUrl;
 
 #[derive(Clone, Debug, JSTraceable, MallocSizeOf, PartialEq)]
 pub enum LoadType {
-    Image(ServoUrl),
-    Script(ServoUrl),
-    Subframe(ServoUrl),
-    Stylesheet(ServoUrl),
-    PageSource(ServoUrl),
+    Image(#[no_trace] ServoUrl),
+    Script(#[no_trace] ServoUrl),
+    Subframe(#[no_trace] ServoUrl),
+    Stylesheet(#[no_trace] ServoUrl),
+    PageSource(#[no_trace] ServoUrl),
     Media,
 }
 
@@ -66,6 +66,7 @@ impl Drop for LoadBlocker {
 
 #[derive(JSTraceable, MallocSizeOf)]
 pub struct DocumentLoader {
+    #[no_trace]
     resource_threads: ResourceThreads,
     blocking_loads: Vec<LoadType>,
     events_inhibited: bool,