Feature Idea: Support pseudo terminal

We recently ran into a case where we'd like to test behavior that is different depending on whether we detect a TTY or not. Currently pycloudlib doesn't [set up a pseudo terminal](https://docs.paramiko.org/en/stable/api/channel.html?highlight=pty#paramiko.channel.Channel.get_pty) for any commands and has no option to do so, so we can't use pycloudlib for this test.

pycloudlib's current behavior is definitely the right default, but it might be useful to support "pty" as an option in pycloudlib for testing this kind of thing.