Support for `native-tls` in client

[mladedav]

I have seen that the support was added to the server in #258, however, I would need to use something different than rustls in the client. This is because there is no cipher that is both in rustls and can be used for connecting to Azure IoT Hub.

[de-sh]

Hey @mladedav, we'd love to include native-tls, are you interested in contributing the same?

[mladedav]

I will see what I can do, but I have never used native-tls and have only a very limitted experience with this crate and rustls (as in I have just tried to make it work earlier this week). So progress may be slow.

I'll see if I can make this work and report here if I do or if I'll need some help.

[de-sh]

This is a continuation of #153