Vulkan: Implement eglBindTexImage Now that vk::ImageHelper is stored as a pointer, it can be shared between an offscreen surface and texture. BUG=angleproject:3073 Change-Id: I91e520259106eef497950b8b2e622fbf910f7444 Reviewed-on: https://chromium-review.googlesource.com/c/1412234 Commit-Queue: Geoff Lang <geofflang@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>