Add mesh shading api to wgpu & wgpu-core

[SupaMaggie70Incorporated]

Connections
#7197

Description
Adds a mesh shading api to wgpu and wgpu-core so that further tests/examples/progress can be made.

This is a rather large PR. If it needs to be split up, I suppose that could be done, but the individual parts all kind of interact. Also doesn't help that I've never tried to split up a branch/PR.

Remaining work is all in limits. There are a lot of limits in https://registry.khronos.org/vulkan/specs/latest/man/html/VkPhysicalDeviceMeshShaderPropertiesEXT.html, many of which will be relevant, though plenty of it for naga. I will only try to use the limits we currently need for validation, rather than try to guess which will be useful.

Testing
This change currently has several tests plus an example.

Squash or Rebase?

Not sure about this honestly, due to inexperience with git.

Checklist

• Run cargo fmt.
• Run taplo format.
• Run cargo clippy. 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.

[SupaMaggie70Incorporated]

This PR got stuck a while back because I was too lazy to go through and understand wgpu's limit system. It should be good to go now. Not sure if we should try to squeeze this in before the 26.0 launch.

[SupaMaggie70Incorporated]

Question regarding mesh shaders in general: is it crucial that good validation is added immediately with PRs? This PR adds some but I suspect that there would be some validation that might be more of a pain to add, and also require some research to determine good defaults/recommended values.

[cwfitzgerald]

Alright have a few comments but the code generally looks reasonable and we should air on the side of merge-and-iterate for something this large, so after these small issues, lets do exactly that!

[cwfitzgerald]

Let's do it!