chore(organizations): improve AWS Organizations service

[MrCloudSec]

Context

Improve AWS Organizations service for a better development of future checks.

Description

• Improve tests.
• Beautify syntax.
• Improve checks.
• Improve Organization Policies structure.

Checklist

• Are there new checks included in this PR? Yes / No
  • If so, do we need to update permissions for the provider? Please review this carefully.
• Review if the code is being covered by tests.
• Review if code is being documented following this specification https://github.com/google/styleguide/blob/gh-pages/pyguide.md#38-comments-and-docstrings
• Review if backport is needed.

License

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov]

Codecov Report

Attention: Patch coverage is 81.63265% with 9 lines in your changes missing coverage. Please review.

Project coverage is 89.17%. Comparing base (1f43e6e) to head (fdddac2).
Report is 7 commits behind head on master.

Files with missing lines	Patch %	Lines
...ny_regions/organizations_scp_check_deny_regions.py	73.33%	8 Missing ⚠️
...ws/services/organizations/organizations_service.py	90.90%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5151      +/-   ##
==========================================
- Coverage   89.19%   89.17%   -0.02%     
==========================================
  Files         976      976              
  Lines       29909    29903       -6     
==========================================
- Hits        26676    26666      -10     
- Misses       3233     3237       +4     

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[pedrooot]

LGTM!