Allow copying one layer of depth/stencil textures

[andyleiserson]

This fixes a regression introduced by #7935.

Multisampled and depth/stencil textures require copying an entire surface, but should not require copying all layers.

Testing
Enables the CTS test that caught the regression in Firefox.

Squash or Rebase? Squash

Checklist

• Run cargo fmt.
• Run taplo format.
• Run cargo clippy --tests. If applicable, add:
  • --target wasm32-unknown-unknown
• Run cargo xtask test to run tests.
• If this contains user-facing changes, add a CHANGELOG.md entry.

[andyleiserson]

Looks like these tests are still failing on Vulkan and Windows. I confirmed that the Vulkan failures existed prior to #7935, but I don't immediately know about Windows.

Edit: and it looks like they're marked as passing on all platforms in Firefox, so something doesn't make sense here.

[teoxoy]

This looks reasonable to me though we should mention "array layer" instead of "mip level" since that's what the depth_or_array_layers represents for these textures.

It is odd that the tests are not passing on Windows - but it could be that it's only reproducible on WARP and not the GPUs we have in Mozilla's CI.

[andyleiserson]

On both Vulkan and dx12, the tests actually pass if run separately rather than in combination. I filed #8021 for this and put them in the list separately for now.