Bugfix/1621 Improve AWS unused credential issue flagging

[rieck-srlabs]

Description

This PR partly fixes #1621

With the changes, ScoutSuite ignores inactive / disabled credentials for the "Credentials Unused for 90 Days or Greater Are Not Disabled" rule in ScoutSuite. The change does not address point 3 of the issue, namely:

3. (Active access keys that have recently been used are also highlighted in red, as long as there is another access key that has not been used recently. Note that this problem is not highlighted in the screenshot above)

I don't believe this last point can feasibly be addressed, as the HTML frontend would need to know about the configurable argument to the rule.

Type of change

Select the relevant option(s):

• 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 not work as expected)
• This change requires a documentation update

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works (optional)
• New and existing unit tests pass locally with my changes

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 20.56%. Comparing base (7a6e3c7) to head (e500930).

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #1623   +/-   ##
========================================
  Coverage    20.56%   20.56%           
========================================
  Files          385      385           
  Lines        13067    13065    -2     
========================================
  Hits          2687     2687           
+ Misses       10380    10378    -2     

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