[graphite] Dst copy tasks stored in DrawTask not root Recorder task list

This keeps the copy task next to the renderpass task whether or not
it's for a regular surface (whose tasks all go to the root anyways)
or for a scratch surface (whose tasks will eventually be only linked
as child tasks).

Bug: b/333052235
Change-Id: I9d612abbc9574dcda98d7ad76834c3c53a15bc78
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/845340
Reviewed-by: James Godfrey-Kittle <jamesgk@google.com>
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
4 files changed