Revert of Simplify SkGpuBlurUtils::GaussianBlur method (patchset #2 id:20001 of https://codereview.chromium.org/1958603002/ )

Reason for revert:
Looks like it's causing some issues with the bleed_image GM.

Original issue's description:
> Simplify SkGpuBlurUtils::GaussianBlur method
>
> No one was using the canClobberSrc capability and moving the direct filtering case forward makes the rest of the logic simpler.
>
> Split out of: https://codereview.chromium.org/1959493002/ (Retract GrRenderTarget from SkGpuBlurUtils)
>
> GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1958603002
>
> Committed: https://skia.googlesource.com/skia/+/56a85e69a8d034e0fdee00e8207cda0a9da06fee

TBR=bsalomon@google.com,robertphillips@google.com
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Review-Url: https://codereview.chromium.org/1956023002
6 files changed