Making D3D12 accept InternalUsageDescriptors

This is a follow up from two previous CLs,
https://dawn-review.googlesource.com/c/dawn/+/58440
and
https://dawn-review.googlesource.com/c/dawn/+/58140

This CL adds in the D3D12Backend the possibility to use Dawn Texture
Internal Usage Descriptor, and adds a series of tests to validate it.

Change-Id: I94f6b39153b60ec8af61bda22d41a865898da613
Bug: dawn:1027, dawn:1052
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/61520
Commit-Queue: Juanmi Huertas <juanmihd@chromium.org>
Reviewed-by: Kai Ninomiya <kainino@chromium.org>

src/include/dawn_native/D3D12Backend.h

@@ -79,6 +79,7 @@ namespace dawn_native { namespace d3d12 {
         // Contents of WGPUTextureDescriptor are stored individually since the descriptor
         // could outlive this image.
         WGPUTextureUsageFlags mUsage;
+        WGPUTextureUsageFlags mUsageInternal = WGPUTextureUsage_None;
         WGPUTextureDimension mDimension;
         WGPUExtent3D mSize;
         WGPUTextureFormat mFormat;