setu32::test_alloc_failures encounters UB, will fail in Rust 1.82

[saethlin]

I am filing this issue because this project's tests failed in the crater runs for Rust 1.82: rust-lang/rust#130579, you can reproduce this failure with cargo +beta test or cargo +nightly test.

The root cause of this is that at least with_capacity_and_bits is unsound; Layout::from_size_align_unchecked documents a precondition that the allocation size must not exceed isize::MAX: https://doc.rust-lang.org/1.81.0/std/alloc/struct.Layout.html#method.from_size_align, and the now-failing test tries to pass an allocation size of isize::MAX + 1.

[droundy]

Thanks for the bug report!