Add glue to link the GrContext createCompressedBackendTexture API to the GL and Vulkan backends

Bug: skia:9680
Change-Id: I05230ec8fd4f9733ba868fd595b163a79c30d32a
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/261081
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
7 files changed