[graphite] Dst reads using copies

Bug: b/238756861
Change-Id: I153b06e2a1f0a0774a19b5f7bdf712abbef3ea0c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/651437
Reviewed-by: John Stiles <johnstiles@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: James Godfrey-Kittle <jamesgk@google.com>
18 files changed