[Blink] Remove HTMLCanvasElement::DisableAccelerationForCanvas2D()

Inline it in CanvasRenderingContext2D::DisableAcceleration(), which is
now its only caller. This enables both removing this Canvas2D-specific
method from HTMLCanvasElement and removing the Canvas2D-specific
DropAndRecreateExistingResourceProviderForCanvas2D() from
CanvasRenderingContext.

Note: At this time we need to leave in an OnAcceleratedDisabled() call
on the canvas. We are going to keep working to incrementally move
tracking of 2d canvas acceleration into the 2d context(s), which will
eventually result in this call no longer being necessary because we will
track the state in the 2d context instead.

Bug: 352263194
Change-Id: I58dec03b49cecfe2d4646ed7c47963a4fd2ab980
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7035731
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Colin Blundell <blundell@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1529347}