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/canvasrenderingcontext2d.rs

@@ -153,6 +153,10 @@ impl CanvasContext for CanvasRenderingContext2D {
         self.set_canvas_bitmap_dimensions(self.size().cast())
     }
 
+    fn reset_bitmap(&self) {
+        self.canvas_state.reset_bitmap()
+    }
+
     fn get_image_data(&self) -> Option<Snapshot> {
         if !self.canvas_state.is_paintable() {
             return None;