* Allow unconsumed inputs in fragment shaders by removing them from vertex
outputs when generating HLSL.
Fixes https://github.com/gfx-rs/wgpu/issues/3748
* Add naga:🔙:hlsl::FragmentEntryPoint for providing information
about the fragment entry point when generating vertex entry points via
naga:🔙:hlsl::Writer::write. Vertex outputs not consumed by the
fragment entry point are omitted in the final output struct.
* Add naga snapshot test for this new feature,
* Remove Features::SHADER_UNUSED_VERTEX_OUTPUT,
StageError::InputNotConsumed, and associated validation logic.
* Make wgpu dx12 backend pass fragment shader info when generating
vertex HLSL.
* Add wgpu regression test for allowing unconsumed inputs.
* Address review
* Add note that nesting structs for the inter-stage interface can't
happen.
* Remove new TODO notes (some addressed and some transferred to an issue
https://github.com/gfx-rs/wgpu/issues/5577)
* Changed issue that regression test refers to 3748 -> 5553
* Add debug_assert that binding.is_some() in hlsl writer
* Fix typos caught in CI
Also, fix compiling snapshot test when hlsl-out feature is not enabled.
