DXIL & HLSL passthrough

[SupaMaggie70Incorporated]

Connections
#7515

Description
This PR adds support for HLSL and DXIL passthrough. This should also move us slightly more towards a precompiled-shader future.

Testing
No tests at the moment. This is the same as MSL. I can add some in the future. However, I don't know how I should store the compiled DXIL in tree. It seems like bad policy to store arbitrary DXIL blobs, but there is no assembly-like thing, which is what I would use for SPIR-V.

Squash or Rebase?
Squash pls

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.

[cwfitzgerald]

However, I don't know how I should store the compiled DXIL in tree. It seems like bad policy to store arbitrary DXIL blobs, but there is no assembly-like thing, which is what I would use for SPIR-V.

So tests are allowed to assume that all of the vulkan sdk is in path, so the test can shell out to dxc to compile HLSL in-tree to DXIL - this way too a single source can be used for both tests.

[cwfitzgerald]

Looking good, some comments

[SupaMaggie70Incorporated]

@cwfitzgerald Everything should be addressed!