Mesh shader HLSL writer

[inner-daemons]

Connections
#7197
Related to #8739

Description
Adds support for mesh shaders to HLSL writer. There still exist some issues:

• Disable some mesh outputs that are unused in the fragment shader
• Clean up code
• Report bugs found while writing
• Limit dispatched workgroup counts
• Only expose mesh shader feature on DX12 if DXC with shader model is supported
• Require shader model 6.5 in naga

Testing
Existing tests, snapshots

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.