Revert: Don't use bytemuck derive on spirv.

[Firestar99]

stacked spirv PR 3/3:

• spirv: derive Hash and impl AsRef #675
• spirv: vector attribute #676
• this PR
• rust-gpu integration: abi: Make glam types abi layout match CPU Rust-GPU/rust-gpu#380

Objective

• Revert Don't use bytemuck derive on spirv. #663
• by this point, all spirv feature gates have been eliminated, apart from #[cfg_attr(target_arch = "spirv", rust_gpu::vector::v1)]

[bitshifter]

I think you'll need to rebase with main and update the PR to resolve conflicts.