Add type hints to scan

[gruebel]

What does this PR do?

I added type hints to all Python methods in cloudsplaining.scan and also refactored some code parts, where possible. I changed the code pretty often to use list/dict comprehension, which is faster than just doing for loops.

What gif best describes this PR or how it makes you feel?

Completion checklist

• Additions and changes have unit tests
• The pull request has been appropriately labeled using the provided PR labels
• GitHub actions automation is passing (make test, make lint, make security-test, make test-js)
• If the UI contents or JavaScript files have been modified, generate a new example report:

[kmcquade]

Fantastic! Super helpful, thank you :)