Revert "Added SkImage::MakeCrossContextFromEncoded"

Revert "Added SkImage::MakeCrossContextFromEncoded"

This reverts commit 83b1b3db36e8622f4bbc8c391d5c714e258d1e03.

Reason for revert: unit test failing and asan leaks

Original change's description:
> Added SkImage::MakeCrossContextFromEncoded
>
> Designed for Flutter's threading architecture, with
> an eye to being useful to other clients. Under the
> hood, uses a new image generator class to lazily wrap
> a texture for multiple GrContexts.
>
> Bug: skia:
> Change-Id: I6c37b12c8ab5bce94b91190e5f0beb91d31ae81b
> Reviewed-on: https://skia-review.googlesource.com/14180
> Commit-Queue: Brian Osman <brianosman@google.com>
> Reviewed-by: Brian Salomon <bsalomon@google.com>
>

TBR=egdaniel@google.com,bsalomon@google.com,robertphillips@google.com,brianosman@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Change-Id: I1f0bf580aa0ea2d132e18b64ff610ddac9d073a7
Reviewed-on: https://skia-review.googlesource.com/15892
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>