Update conf-libssl for the mingw-w64 ports

[dra27]

This commit is extracted from the opam 2.2.0 Windows announcement is intended in part to serve as a demonstration of the changes which need to be made to conf- packages to support the opam 2.2.0 depext scheme for native Windows following the merge of #25861.

The key parts:

• Constraining old versions of conf- packages
• Adding conf-mingw-w64-* packages for each architecture with MSYS2 and Cygwin package names
• Updating the latest version of the main conf- package with a dependency formula and adapting pkg-config to use --personality, etc.

[mseri]

Wow, that is quite involved, it will make it hard to review and understand them

[dra27]

Indeed, although it should be largely one-time pain (it's not like the conf- packages get materially updated that frequently) and, as in #26102, I'm very happy to be pinged to review them (even if that's slightly weird for the ones I've actually opened!)