Update GL and Vulkan backends to support compressed backend formats

We're running out of pretty ways to split up the omnibus CL. This just
brute force updates the two working backends (sorry Metal).

Bug: skia:9680
Change-Id: I62ce1229ff40e3d4e194337f2fe0acddb3f934e5
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/260897
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
4 files changed