Added option to show controllers optionally in the router:debug command

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Added option to show controllers in the router debug command as a convenience function.

    app/console router:debug --show-controllers