Make createTestingOnlyBackendTexture and deleteTestingOnlyBackendTexture no longer be behind GR_TEST_UTILS (take 2)

Change-Id: Id00d0692c99c7eaec685788fec29ee189f020f2f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/214180
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
10 files changed