Vulkan: Add check for VK_EXT_external_memory_host extension Tests-Passing: GN Build Bug: angleproject:42266936 Change-Id: Ie30f1cee939bc8a4b98d37f718e4526156916f05 Signed-off-by: Rafay Khurram <r.khurram@samsung.com> Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/5796524 Reviewed-by: Geoff Lang <geofflang@chromium.org> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>