Vulkan: Expose extension for ETC1 usage with subimage updates This CL implements the GL_EXT_compressed_ETC1_RGB8_sub_texture extension, which was added to relax restrictions on using ETC1_RGB8_OES for subimage updates. Test: Temple Run on Android Bug: b:152512564 Change-Id: I78cfd7dfd54fab36dee59a93b3ec3bfce17e73e4 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2123232 Commit-Queue: Cody Northrop <cnorthrop@google.com> Reviewed-by: Geoff Lang <geofflang@chromium.org>