Switch to `openssl rehash` instead of `c_rehash` for custom certificate management

The following discussion from !5765 (merged) should be addressed:

Side note, once we drop rhel 7 support, or decide we won't offer system ssl packages for rhel 7, we can switch from c_rehash to openssl rehash

New findings

From @rmarshall :

I was investigating the auto-dependency update for OpenSSL created by our dependencies automation in !6080 (merged) when I found CVE-2022-1292.

Discussed with @WarheadsSE during our coffee chat today, and we think that the best path is to make this change and backport it rather than backporting OpenSSL 1.1.1o.