Add Entry points for GL_EXT_EGL_image_storage Code generation for GL_EXT_EGL_image_storage Bug: angleproject:6346 Change-Id: Ib918619205bfe7bd8fba0748ff6db593c858151f Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3133763 Commit-Queue: Brandon Schade <b.schade@samsung.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>