Spirv passthrough main (adopted, part deux)

[bas-ie]

Note: This is an adoption of @Shfty 's adoption (#8131) of #3996! All I've done is updated the branch and run the docs CI.

Note: This is an adoption of #3996, originally authored by @molikto

Objective

Allow use of wgpu::Features::SPIRV_SHADER_PASSTHROUGH and the corresponding wgpu::Device::create_shader_module_spirv for SPIR-V shader assets.

This enables use-cases where naga is not sufficient to load a given (valid) SPIR-V module, i.e. cases where naga lacks support for a given SPIR-V feature employed by a third-party codegen backend like rust-gpu.

Solution

• Reimplemented the changes from Spirv shader bypass #3996, on account of the original branch having been deleted.
• Documented the new spirv_shader_passthrough feature flag with the appropriate platform support context from wgpu's documentation.

Changelog

• Adds a spirv_shader_passthrough feature flag to the following crates:

  • bevy
  • bevy_internal
  • bevy_render

• Extends RenderDevice::create_shader_module with a conditional call to wgpu::Device::create_shader_module_spirv if spirv_shader_passthrough is enabled and wgpu::Features::SPIRV_SHADER_PASSTHROUGH is present for the current platform.

• Documents the relevant wgpu platform support in docs/cargo_features.md