Apparently some providers fail TLS connection
with "no_application_protocol" alert
even when requesting "imap" protocol for IMAP connection
and "smtp" protocol for SMTP connection.
Fixes <https://github.com/deltachat/deltachat-core-rust/issues/5892>.
Single function smtp::connect::connect_stream
returns a stream of a single `dyn` type
that can be a TLS, STARTTLS or plaintext
connection established over SOCKS5 or directly.