[graphite] Don't go through Recording for Context's asyncReadPixels

Bug: b/238790417
Bug: skia:13898
Change-Id: I393c7c0aad13a1d344c1889eba980498909f08d1
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/608177
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
9 files changed