PbufferSurfaces are now created with VK_KHR_image_format_list
extension support enabled.

Bug: angleproject:2514
Bug: angleproject:5281
Test: PbufferTest.ClearAndBindTexImageSrgb*Vulkan
Change-Id: I8977484c958328d00f688faa7adffff85a37a3b8
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2530535
Commit-Queue: Mohan Maiya <m.maiya@samsung.com>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>