Support exit_country with handle_socks_conn

At the moment it is not possible to specify an exit country for socks usage, since the prefs are getting created from socks info only (https://gitlab.torproject.org/tpo/core/arti/-/blob/main/crates/arti/src/socks.rs#L67). The country_code seems to be at an impractical position for some use cases. The default connect_prefs of the TorClient are also not getting inherited.

Is there probably another way how to specify the country in a way it will work with socks?