8dabf5da9e
simplify layout calculations in rawvec The use of `Layout::array` was introduced in #83706 which lead to a [perf regression](https://github.com/rust-lang/rust/pull/83706#issuecomment-1048377719). This PR basically reverts that change since rust currently only supports stride == size types, but to be on the safe side it leaves a const-assert there to make sure this gets caught if those assumptions ever change.