Allow Naga spv-in and spv-out in no_std

[bushrat011899]

Connections

• Contributes to Support no_std where possible (specifically for wasm32v1-none) #6826

Description

• Removed spv-in and spv-out from the std configuration of Naga.
• Added a fs feature to Naga for integration with std::fs (currently only used to write block context dumps in SPIR-V)
• Adjusted internal usage of Path and PathBuf to add one layer of indirection, allowing Naga to choose either Path/Buf or str/String for internal storage based on std availability. This is only required in spv::Options and spv::DebugInfo, but the technique may be suitable to extract into wgpu-types if required in other areas.
• Added spv-in and spv-out to the Naga component of the no_std CI task.

Testing

• CI

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.

[cwfitzgerald]

Some notes

[cwfitzgerald]

Both this and the other struct should be in a common place in naga so it can be re-used throughout the codebase, instead of isolated to spv frontend/backend.

[bushrat011899]

Agreed. I've moved these into naga::path_like (which is a rename of naga::as_diagnostic_file_path). I've kept the types public in a private module as we don't intend for other crates to rely on these types. But I'm happy to move this whole module into wgpu-types and make it public if you'd prefer.