Now is common between CliBehaviour and ServBehaviour

Thanks to bruh![moment] on Discord for details how to make it work

Improve the roundtrip pubkey auth test

std and picow embassy server demos work, no channels yet

Work in progress, can probably be simplified

Add missing Cargo files for picow
Add "log" for embassy

Wifi parts based on the example in https://github.com/embassy-rs/cyw43/

Not yet working

Don't require Behaviour to be Send

This needs to go upstream as a crate dependency

Moved sshproto to a top level source directory

No changes yet, but is necessary to configure algorithm lists