Fixes #12200

Description
Fortify FPR artifacts can contain an additional audit.xml file which contains audit/triage data made by users. One possible outcome is that vulnerabilities are suppressed. These are now marked as False Positive (and active=False) in DefectDojo.
These vulnerabilities typically have comments in the audit.xml. These are added to the impact field.

Test results
Added unit test.

Documentation
Added note to existing docs.

Checklist

• Make sure to rebase your PR against the very latest dev.
• Features/Changes should be submitted against the dev.
• Bugfixes should be submitted against the bugfix branch.
• Give a meaningful name to your PR, as it may end up being used in the release notes.
• Your code is flake8 compliant.
• Your code is python 3.11 compliant.
• If this is a new feature and not a bug fix, you've included the proper documentation in the docs at https://github.com/DefectDojo/django-DefectDojo/tree/dev/docs as part of this PR.
• Model changes must include the necessary migrations in the dojo/db_migrations folder.
• Add applicable tests to the unit tests.
• Add the proper label to categorize your PR.