Auto merge of #19755 - streichgeorg:decoupling_metrics_gfx, r=jdm

Decouple metrics and gfx

Added gfx_traits::DisplayList so metrics doesn't depend on the gfx crate for gfx::display_list::DisplayList.

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components/layout_thread/lib.rs

@@ -1042,7 +1042,7 @@ impl LayoutThread {
             // Observe notifications about rendered frames if needed right before
             // sending the display list to WebRender in order to set time related
             // Progressive Web Metrics.
-            self.paint_time_metrics.maybe_observe_paint_time(self, epoch, &display_list);
+            self.paint_time_metrics.maybe_observe_paint_time(self, epoch, &*display_list);
 
             self.webrender_api.set_display_list(
                 self.webrender_document,