RendererVk: Skip VK_KHR_image_format_list on SwiftShader. Enabling the extension produces timeouts on Linux when running Chromium test suites like viz_unittests with a Debug configuration. Bug: angleproject:5281 Bug: chromium:1245774 Change-Id: I6241597dfe0300f3793524d5a73a4ef2cf0dc4eb Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3140158 Commit-Queue: Lubosz Sarnecki <lubosz.sarnecki@collabora.com> Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>