Boring 5 Roadmap

[nox]

Now that boring 4 is pretty old (I'm just joking), let's keep track of what we should do for boring 5:

• hyper-boring: update to hyper 1.0.0 #194
• Rename replace_ex_data to set_ex_data, as keeping the leaking versions is a footgun
• Rename Ssl::new_from_ref to Ssl::new
• Rename X509Builder::append_extension2 to X509Builder::append_extension
• Make boring::ssl::SslStream::new infallible, its current return type is Result<_, ErrorStack> but it returns Ok(_) always.
• Remove obsolete X509CheckFlags values

[howardjohn]

Any alternative (or addition, I suppose) to hyper 1.0 support could be #165, which lets the rest of the rustls ecosystem handle things like tokio, hyper, etc integration