Allow vendoring rust-openssl as it now supports 3.x.x versions

[pmarr]

Is your feature request related to a problem? Please describe.

Building kanidm unix integration on openssl 1.1.X distros requires building webauthn-rs separately with vendored openssl, then building kanidm with a patch to the local webauthn-rs build.

The minimum openssl version needed to compile build-dependencies is 3.x.x based on build time checks from #418. This version is now supported by rust-openssl vendoring.

Describe the solution you'd like

I would like when I enable openssl = { version = "^0.10.56", features = ["vendored"] } at the kanidm workspace Cargo.toml, the build dependency for webauthn-rs also uses this vendored version rather than the host openssl.

Can we set the minimum openssl version to ^3.x.x and enable vendoring?

Describe alternatives you've considered

Please see kanidm/kanidm#2839 (comment)
for the build process of kanidm and webauthn-rs on rhel8 distros.

Additional context

If I am misunderstanding what is needed to happen, forgive me. It sounds like we can vendor rust-openssl and only support openssl v3.x.x for both kanidm and webauthn-rs

Issue #416 adds the docs to mention vendoring is possible

kanidm/kanidm#2839 (reply in thread) @Firstyear asked me to open an issue here and on kanidm/kanidm kanidm/kanidm#3480