Consider making search result re-ordering toggleable per-wiki

[KevinPayravi]

In v3.7.0, we introduced the search engine "re-ordering" feature. This feature moves indie wikis results above the first non-indie result, and if the indie and non-indie results have the same article name, the non-indie result is hidden. The non-indie result is hidden to reduce repetitive results and help ensure clicks are sent to the independent wiki, instead of users relying on the replacement button or redirection.

This feature assumes that the independent wiki's article is as complete and up-to-date as the non-indie wiki, but this is not always the case (see https://github.com/KevinPayravi/indie-wiki-buddy/issues/824 for an example).

Currently, users can toggle this feature via the "Move indie wikis above non-indie results and hide duplicates" setting, which applies to all wikis. Unlike the other search filtering options (hiding / replacing), this feature isn't toggleable per-wiki.

We may want to consider allowing users to toggle this feature per-wiki. The UI for toggling features per-wiki is already quite busy, so we will want to ensure the UI is easily understood and avoid confusion between all the search engine options (hiding, replacing, re-ordering + hiding).