Auto merge of #43217 - pnkfelix:alloc-requires-align-it-in-u32, r=alexcrichton
Add precondition to `Layout` that the `align` fit in a u32.
Add precondition to `Layout` that the `align` not exceed 2^31.
This precondition takes the form of a behavorial change in `Layout::from_size_align` (so it returns `None` if the input `align` is too large) and a new requirement for safe usage of `Layout::from_size_align_unchecked`.
Fix #30170.