[graphite] More testing infrastructure

With this CL we can run as:

     dm --src gm skp tests --config grmtl -v --nocpu --nogpu

and not get all the non-Graphite unit tests.

Bug: skia:12466
Change-Id: Ib3f04f315fe4b5731a54e4c72979a0c1e00baf24
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/457898
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
19 files changed