Drush command test-users:create arguments for roles and password

The argument for user roles is added to the command in the merge request.

Argument for password selection still to be done.

Argument for password also done.

Looks good. I tried whether it is possible to have the roles as separate arguments, but it seems Drush only supports a fixed number of arguments. I did turn the password into an option and added an email domain option while at it.