Move some libssl global variables into SSL_CTX

Move some libssl global variables into SSL_CTX

disabled_enc_mask et al were global. Now that cipher loading is done
individually for each SSL_CTX, based on the libctx configured for that
SSL_CTX this means that some things will be disabled for one SSL_CTX but
not for another. The global variables set up the potential for different
SSL_CTXs to trample on each other. We move these variables into the SSL_CTX
structure.

Fixes #12040

Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Paul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/13465)