GHSA-gv7f-5qqh-vxfx xous has unsound usages of `core::slice::from_raw_parts`

• crates.io xous: < 0.9.51 → fixed in 0.9.51

We consider `as_slice` and `as_slice_mut` unsound because: the pointer with any bit patterns could be cast to the slice of arbitrary types. The pointer could be created by unsafe new and deprecated `from_parts`. We consider that `from_parts` should be removed in latest version because it will help trigger unsoundness in `as_slice`. With new declared as unsafe, `as_slice` should also declared as unsafe. This was patched in by marking two functions as `unsafe`.