Replace getpass with ui.input(hidden=True)

Description

I'm currently trying to automate gimme-aws-creds in a python script. I admire the idea of the gimme_aws_creds.ui.UserInterface class that helps a lot in automating user input. I found that some places in the code was directly calling getpass.getpass() and not using the provided UserInterface. Replacing those calls with the proper UserInterface.input(hidden=True).

Related Issue

Fixes #428

Motivation and Context

Allowing developers subclassing gimme_aws_creds.ui.UserInterface for automation to provide inputs for password themselves.

How Has This Been Tested?

Ran pytest -vv tests with no errors
Tested it with a script mocking the user input via a subclass of UserInterface.

Screenshots (if appropriate):

Types of changes

[x] Bug fix (non-breaking change which fixes an issue)
[ ] New feature (non-breaking change which adds functionality)
[ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

[x] My code follows the code style of this project.
[ ] My change requires a change to the documentation.
[ ] I have updated the documentation accordingly.
[x] I have read the CONTRIBUTING document.
[ ] I have added tests to cover my changes.
[x] All new and existing tests passed.

Nike-Inc / gimme-aws-creds