fonts: Store web fonts in the per-Layout FontContext (#32303)

This moves mangement of web fonts to the per-Layout `FontContext`,
preventing web fonts from being available in different Documents.

Fixes #12920.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>
Co-authored-by: Mukilan Thiyagarajan <mukilan@igalia.com>

components/script/script_thread.rs

@@ -3536,6 +3536,7 @@ impl ScriptThread {
             script_chan: self.control_chan.clone(),
             image_cache: self.image_cache.clone(),
             font_cache_thread: self.font_cache_thread.clone(),
+            resource_threads: self.resource_threads.clone(),
             time_profiler_chan: self.time_profiler_chan.clone(),
             webrender_api_sender: self.webrender_api_sender.clone(),
             paint_time_metrics,