[Blink] Streamline call to EnableAccelerationForCanvas2D()

This call is effectively a no-nop for OffscreenCanvas, as all it does
is call GetOrCreateResourceProviderForCanvas2D() [1], and it is
immediately followed by the same call [2][3][4]. This CL changes it to a
virtual method on BaseRenderingContext2D and has only
CanvasRenderingContext2D implement the virtual method to call through to
the current HTMLCanvasElement method.

[1] https://chromium-review.googlesource.com/c/chromium/src/+/6700510
[2] https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/renderer/modules/canvas/canvas2d/base_rendering_context_2d.cc;l=1498?q=EnableACcelerationFor&ss=chromium
[3] https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/renderer/modules/canvas/offscreencanvas2d/offscreen_canvas_rendering_context_2d.cc;l=418;drc=f70a0969b8b5dea5d99de43de959479d7f9cf603;bpv=1;bpt=1
[4] https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/renderer/modules/canvas/offscreencanvas2d/offscreen_canvas_rendering_context_2d.cc;l=170;drc=f70a0969b8b5dea5d99de43de959479d7f9cf603

Bug: 352263194
Change-Id: Iff02f72166d25d14c48d199b2211dc426b2c5563
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6700809
Commit-Queue: Colin Blundell <blundell@chromium.org>
Reviewed-by: Vasiliy Telezhnikov <vasilyt@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1482076}