Support rustls feature without using ring or aws-lc-rs

[TroyKomodo]

As the title says, support rustls without specifically specifying the underlying provider.

A lot of libraries expose some way of picking the provider but also allow for no provider to be installed.

[djc]

What provider are you trying to use? Would you be able to submit a PR?

[TroyKomodo]

I am working on a seanmonstar/reqwest#2796 and noticed that there is no way to enable rustls in quinn without using a crypto provider. I am not sure if this is possible since i noticed aswell that quinn-proto directly uses ring instead of using it through rustls.

[djc]

@ctz I think you were working in this direction, you had a branch somewhere right? I can't find an earlier issue in this report ATM...

[ctz]

Yep my WIP branch for this is at main...ctz:quinn:jbp-retry-calculation-uses-rustls -- haven't worked on it for a while and can't really remember where I got with it.