[graphite] Clamp-to-border in image shader

Bug: b/238754369
Change-Id: I0440324a617bddd8005abe0bd35a50860509b58e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/581956
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: James Godfrey-Kittle <jamesgk@google.com>
42 files changed