[graphite] Make MatrixConvolutionImageFilter stably keyed (take 2)

Bug: b/238759147
Change-Id: Ie5d8047a292d05311acae31cea4221c9532100e0
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/853096
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
7 files changed