This cl adds support for the VK_KHR_separate_depth_stencil_layouts.
It doesn't add any new functionality, since SwiftShader has
historically supported quad layout stencil and non quad layout depth.

Bug: b/148881874
Change-Id: I6ed77ee1261bfda1468595474cf0840564f2553d
Tests: dEQP-VK.*
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/41068
Presubmit-Ready: Alexis Hétu <sugoi@google.com>
Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>