MFV: crypto/openssl: update to 3.5.6

This change brings in version 3.5.6 of OpenSSL, which features
several security fixes (the highest of which is a MEDIUM severity
issue), as well as some miscellaneous feature updates.

Please see the release notes [1] for more details.

PS Apologies for the confusing merge commits -- I was testing out a
new automated update process and failed to catch the commit message
issues until after I pushed the change.

1. https://github.com/openssl/openssl/blob/openssl-3.5.6/NEWS.md

MFC after: 1 day (the security issues warrant a quick backport).
Merge commit 'ab5fc4ac933ff67bc800e774dffce15e2a541e90'