This extension allows users to query and specify different usages for
the main image and the stencil. SwiftShader does not use an image's
usage for non-debug purposes outside of
vkGetPhysicalDeviceImageFormatProperties2. This applies to separate
stencil usage as well.

Bug: b/176098507
Tests: dEQP-VK.pipeline.sampler.separate_stencil_usage.*
Tests: dEQP-VK.renderpass.suballocation.multisample.separate_stencil_usage.*
Tests: dEQP-VK.renderpass2.suballocation.multisample.separate_stencil_usage.*
Change-Id: Iea74a9fa0de8cdcc51bdc613cdc0754e0f327fd5
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/51368Tested-by: Sean Risser <srisser@google.com>
Commit-Queue: Sean Risser <srisser@google.com>
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>