Conversion between Box<T: Unalign> and Box<[u8]>

[kupiakos]

There's no safe way to no-op convert between allocated bytes and allocated T when T is unaligned and FromBytes + IntoBytes. An Immutable bound is not needed in any case because Box is non-aliasing like &mut.

Future design thinking: what about Rc and Arc? Why is there not impl ByteSlice for Box<T> so it can be used in Ref with looser requirements (T: Unalign is no longer needed)?