VK_EXT_metal_surface is a similar extension to VK_MVK_macos_surface,
which is already supported.

Bug: chromium:1015454
Change-Id: I08d8e6b097d75236f724984b8c7d20251a63581f
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/37808
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Tested-by: Jonah Ryan-Davis <jonahr@google.com>