Crypto provider support

[stevefan1999-personal]

Given that rustls/rustls#1405 is closer to completion, we need to think about crypto provider support.

We could still provide ring provider out of the box (I think rustls would in the end include ring as part of the default options to prevent chaos), but this would render custom crypto provider useless due to tokio-rustls usually being a transient dependency (for example axum_server usestokio-rustls) and I don't think there is a way to patch the transient dependency of axum_server without forking it.

[djc]

Like rustls, we will make ring a feature that is enabled by default in the next semver-breaking release. axum_server will then need to do the same.

[richarddd]

rustls has now extracted crypto provider into separate dependency. Can we do the same here? 🙂

[cpu]

I believe this has been handled w/ 0.25:

ring is enabled by default but can be disabled. If you disable that feature and construct your Client/Server configs using the _with_provider fns you can provide your own non-default crypto provider.