Merge SkGpuBlurUtils into GrBlurUtils

If there are functions that need to be used in Graphite as well,
(e.g. Compute1DLinearGaussianKernel) I suggest making
src/gpu/BlurUtils.h for those.

Change-Id: Ie3b32d5d0a23b89aada516122071f15896ed5fb2
Bug: skia:14317
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/723341
Commit-Queue: Kevin Lubick <kjlubick@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
13 files changed