[nanorand] Aliased mutable references from `tls_rand` & `TlsWyRand`

TlsWyRand‘s implementation of Deref unconditionally dereferences a raw pointer, and returns
multiple mutable references to the same object, which is undefined behavior.

References

• https://github.com/Absolucy/nanorand-rs/issues/28
• https://rustsec.org/advisories/RUSTSEC-2021-0114.html
• https://github.com/advisories/GHSA-p6gj-gpc8-f8xw