This implements the extension defined here:
https://www.khronos.org/registry/vulkan/specs/1.2-extensions/man/html/VK_EXT_headless_surface.html

This extension is useful for tests/benchmarks as it provides a way to
create a platform-agnostic Surface with Swapchain, etc., instead of
having to create an non-visible framebuffer.

Bug: b/176981107
Change-Id: Iad1e55ed7a4e32cebf7577d9d88a9aed4b6f7a20
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/51589Tested-by: Antonio Maiorano <amaiorano@google.com>
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Commit-Queue: Antonio Maiorano <amaiorano@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>