Reland "Revert "Fix tile modes in SkGpuBlurUtils.""

This reverts commit e5865f6f10d969aefbec2dcb6975fbe5c3c6059e.

Reason for revert: some async GMs on some configs look like they are
reading from edges of approx textures.

Original change's description:
> Revert "Revert "Fix tile modes in SkGpuBlurUtils.""
> 
> This reverts commit 88d04cb51acfb7d8b92895270fa58e266d9522c6.
> 
> Change-Id: I3ca403bb9631a273b5cbe2304c6c3ff9dd01fa89
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/289625
> Reviewed-by: Michael Ludwig <michaelludwig@google.com>
> Commit-Queue: Brian Salomon <bsalomon@google.com>

TBR=bsalomon@google.com,michaelludwig@google.com

# Not skipping CQ checks because this is a reland.

Change-Id: If6f5917982b8c865161e7f4a566df49cb772989b
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/290036
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
12 files changed