Fix wgsl out struct layout

[mikialex]

fix gfx-rs/wgpu#4373 by explicitly adding a size mark on all struct fields.

[mikialex]

a test failed due to the two struct field members having the same offset. I think this should be checked in validation and fixed in another pr.

[teoxoy]

We can avoid writing the size explicitly if it's the same as the one inferred. See example below on how to get the size:

naga/src/back/msl/writer.rs

Lines 3178 to 3179 in 0491d39

	let ty_inner = &module.types[member.ty].inner;
	last_offset = member.offset + ty_inner.size(module.to_ctx());

[cwfitzgerald]

Hello, thank you for your PR against Naga!

As part of gfx-rs/wgpu#4231, we have moved development of Naga into the wgpu repository in the Naga subfolder. We have transferred all issues, but we are unable to automatically transfer PRs.

As such, please recreate your PR against the wgpu repository. We apologize for the inconvenience this causes, but will make contributing to both projects more streamlined going forward.

We are leaving PRs open, but once they are transferred, please close the original Naga PR.