Fix a memory leak with di2_X509_CRL reuse

Additionally avoid undefined behavior with
in-place memcpy in X509_CRL_digest.

Fixes #8099

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/8112)

(cherry picked from commit a727627922b8a9ec6628ffaa2054b4b3833d674b)