Use existing input object when calling init_tab_complete

[sjanusz-r7]

This PR changes the input class used by the Driver to be Rex Readline instead of Rex Stdio.
It also changes the init_tab_complete method to no longer overwrite the currently existing self.input object but to instead reset its tab completion.

The original code originated around 2005, with no reason given as to why init_tab_complete would need to overwrite the Stdio object with Readline.new(lambda ...). This also fixes the scenario of the self.input object being overwritten if passed in as an option to the Driver constructor and then calling the init_tab_complete method.

Verification

List the steps needed to make sure this thing works

• Start msfconsole
• Ensure you can use the console as expected
• Ensure tab completion works as expected
• CI passes