Make rcu_thread_key context-aware

Make rcu_thread_key context-aware

Currently, rcu has a global bit of data, the CRYPTO_THREAD_LOCAL object
to store per thread data.  This works in some cases, but fails in FIPS,
becuase it contains its own copy of the global key.

So
1) Make the rcu_thr_key a per-context variable, and force
   ossl_rcu_lock_new to be context aware

2) Store a pointer to the context in the lock object

3) Use the context to get the global thread key on read/write lock

4) Use ossl_thread_start_init to properly register a cleanup on thread
   exit

5) Fix up missed calls to OSSL_thread_stop() in our tests

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/24162)