History: Orphan preferences

New in Tiki25, it permits to clean out Preferences for previously used but later removed features in Tiki.

As of Tiki25, please consider this feature as experimental. Only use it if you are an experienced Tiki administrator.

There is likely some data here that is actually still used, but in a non-standard way, so it fools our script.

Initial commit:
https://gitlab.com/tikiwiki/tiki/-/merge_requests/1798