Add password reporting API to external modules

[acammack-r7]

This adds an API to the external module interface capable of reporting correct and incorrect passwords. Also, some refactoring of the API was done to make some things easier to use and (hopefully) more reliable.

Verification (creds)

• Throw populate_creds.py into ~/.msf4/modules/auxiliary/test/scanner/load_creds.py and chmod +x. https://gist.github.com/acammack-r7/06fc0ede7869d5b28497805bc0e11718
• Throw creds.txt into /tmp
• ./msfconsole
• workspace -a pr10002
• use auxiliary/test/scanner/load_creds
• set rhosts 127.0.0.1
• set user_file /tmp/creds.txt
• set pass_file /tmp/creds.txt
• run
• All password combinations should be tried and fail with duplicates not attempted
• creds should be empty
• edit and change False to True in the valid_login function
• run
• All password combinations should be tried and work with duplicates not attempted
• creds should have all the passwords

Verification (refactor)

• Make sure your favorite external modules still works as expected
• ex, the Haraka steps from Add support for non-Ruby modules #8178
• or ROBOT: Add scanner for the Bleichenbacker oracle (AKA: ROBOT) #9489
• or SharknAT&To Add SharknAT&To scanner #9424

[asoto-r7]

Worked perfectly -- thanks!

Just fixed ause use typo above, and now I understand that specifying the PYTHONPATH environment variable isn't required.

[asoto-r7]

Release Notes

The external module interface now includes an API for reporting correct and incorrect passwords.