Add features of depth24unorm-stencil8 and depth32float-stencil8 texture formats

The depth240unorm-stencil8 and depth32float-stencil8 are optional
features. Enable them and add validation tests for texture creation
and texture view creation.

They are unimplmented on backends, skip their end2end tests.

TODO: add validtion for copy commands.

BUG=dawn:690

Change-Id: I980631d2f3fa6397a6125221a76980a15c8cb2f5
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/68220
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: Hao Li <hao.x.li@intel.com>

src/dawn_native/Features.h

@@ -31,6 +31,8 @@ namespace dawn_native {
         PipelineStatisticsQuery,
         TimestampQuery,
         DepthClamping,
+        Depth24UnormStencil8,
+        Depth32FloatStencil8,
 
         // Dawn-specific
         DawnInternalUsages,