Memory layout #3
Description
Often it's enough to just get the memory layout from naga and work with that. But we might also just be able to get size and alignment of e.g. a VectorType. This is complicated by the fact that vectors can be represented with SIMD or not, though the memory layout should not change, just the way IR values are stored and loaded.
This also interacts with how values are loaded, stored and member references are constructed.