Fixes #38932 - Allow users to purge all audit types

[ekohl]

The various template types are excluded from foreman-rake audits:clean because they're also used to show diffs to older versions. These can build up over time and users need a way to clean these up.

This introduces the AUDITS_PURGE_INCLUDE_TEMPLATES environment variable to purge all audit types.

Currently untested so this is a draft.