Move OCSP stapling information from a per-certificate store (ex_data attached to an X509 *) to a per-server hash which is allocated from the pconf pool. Fixes PR 54357, PR 56919 and a leak with the certinfo_free cleanup function (missing OCSP_CERTID_free).
* modules/ssl/ssl_util_stapling.c: drop certinfo_free, and add ssl_stapling_certid_free (used with apr_pool_cleanup_register). Switch to a stapling_certinfo hash which is keyed by the SHA-1 digest of the certificate's DER encoding, rework ssl_stapling_init_cert to only store info once per certificate (allocated from the pconf to the extent possible) and extend the logging.
* modules/ssl/ssl_private.h: adjust prototype for ssl_stapling_init_cert, replace ssl_stapling_ex_init with ssl_stapling_certinfo_hash_init