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>
