Revert "Remove code to push pixmaps to backend textures from GrGpu classes"

This reverts commit 45889d12696f8e0af2796a6bbd3938b6d2614eca.

Reason for revert: compressed texture assertion on D3D bot

Original change's description:
> Remove code to push pixmaps to backend textures from GrGpu classes
>
> Replace GrGpu::updateBackendTexture with narrower method that clears
> a backend texture.
>
> Creation of data for a solid color compressed texture is lifted up to
> GrDirectContext and goes through updateCompressedBackendTexture.
>
> Bug: skia:11786
> Change-Id: I1d617623df5e65686f30e57c361a64f78d77f7bd
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/392836
> Reviewed-by: Jim Van Verth <jvanverth@google.com>
> Reviewed-by: Greg Daniel <egdaniel@google.com>
> Commit-Queue: Brian Salomon <bsalomon@google.com>

TBR=egdaniel@google.com,jvanverth@google.com,bsalomon@google.com

Change-Id: Ie58f52245c44c77f09742b0cb590cc97b97e6e37
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:11786
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/396097
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
18 files changed