wgsl: Validate various structs with size/align validate correctly.

[dj2]

Create tests with various combinations of size and align on the struct members to see that things parse correctly.

• [ ] size to odd numbers of bytes and add aligns for various types of elements
• [ ] nested struct with huge odd size
• [ ] vec3<f32>; f32 or f32; vec3<f32> (first could be tucked together in other languages)
• [ ] mat2x3<f32> and mat3x2<f32>
• [ ] vec3<f16>
• [ ] array with element count
• [ ] runtime array
• [ ] array of structs of odd size