Vulkan: Move renderer to namespace vk This class is agnostic of EGL. This change moves it to namespace vk for use with the OpenCL implementation Bug: angleproject:8564 Change-Id: I57f7807d6af8b3d5d7f8efbaf8b5d537a930f881 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/5371324 Reviewed-by: Austin Annestrand <a.annestrand@samsung.com> Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>