Make createTestingOnlyBackendTexture and deleteTestingOnlyBackendTexture no longer be behind GR_TEST_UTILS

Change-Id: Iec44bc46aa2ab2899af3f6df130a93adf3f26e2a
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/213821
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
9 files changed