ANGLE needs to be able to use the depth buffer in a sampled
texture to emulate some GLES2 features, even when the image
also contains a stencil. Added support for sampling the
depth+stencil format we support.

Tests: dEQP-VK.*

Bug b/141304420

Change-Id: Ia4ccce2a155aa16178f16eb92efae9fc357b6e45
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/36449
Presubmit-Ready: Alexis Hétu <sugoi@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>