Convert hashtable to using ossl_rcu_deref on lookup

Convert hashtable to using ossl_rcu_deref on lookup

The new hashtable has an issue on non-64 bit builds.  We use
CRYPTO_atomic_load to load a pointer value when doing lookups, but that
API relies on the expectation that pointers are 64 bits wide.  On 32 bit
systems, we try to load 64 bits using CRYPTO_atomic_load into a 32 bit
pointer, which overruns our stack

Fix this by no longer using CRYPTO_atomic_load for value fetches from
the hashtable.  Instead use ossl_rcu_deref, whcih operates on void
pointers and is safe on all arches

Reviewed-by: Paul Dale <ppzgs1@gmail.com>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/24682)