Add option for fully interactive shell

[clubby789]

Whenever I use pwntools to gain a shell, and call interactive() it can be frustrating to deal with not being able to use Ctrl-C, Ctrl-Z etc. I believe it would be useful to add a tty flag to interactive() so it handles keyboard events such as these without exiting.

[Arusekk]

This could possibly be solved if the remote end was shell, we could spawn a pty on remote end and route keystrokes through it... but it is way harder than just installing a signal handler on local side / manipulating termios stuff.

[Arusekk]

This might be actually possible as in rapid7/metasploit-framework#10389 (we already have a dealarm function)