Use the new hashtable for core_namemap

Use the new hashtable for core_namemap

This replaces LHASH in core_namemap with the new hashtable and adds
a reverse mapping in form of stack of stacks instead of iterating
the existing hash table members.

The new hashtable is used in lockless-read mode.

Reviewed-by: Neil Horman <nhorman@openssl.org>
Reviewed-by: Paul Dale <ppzgs1@gmail.com>
(Merged from https://github.com/openssl/openssl/pull/24504)