canvas: Add OffscreenCanvas 'transferToImageBitmap' method (#37880)

Follow the HTML speficication and add missing 'transferToImageBitmap'
method to OffscreenCanvas interface.

https://html.spec.whatwg.org/multipage/#dom-offscreencanvas-transfertoimagebitmap

Testing: Improvements in the following tests
- html/canvas/offscreen/compositing/2d.composite.grid*
- html/canvas/offscreen/fill-and-stroke-styles/2d.gradient*
- html/canvas/offscreen/manual/the-offscreen-canvas/offscreencanvas*
- html/canvas/offscreen/reset/2d.reset*
- html/canvas/offscreen/text/2d.text*

Fixes (partially): #34111

Signed-off-by: Andrei Volykhin <andrei.volykhin@gmail.com>

components/script/dom/webgl2renderingcontext.rs

@@ -916,6 +916,10 @@ impl CanvasContext for WebGL2RenderingContext {
         self.base.resize();
     }
 
+    fn reset_bitmap(&self) {
+        self.base.reset_bitmap();
+    }
+
     fn get_image_data(&self) -> Option<Snapshot> {
         self.base.get_image_data()
     }