* New possibility to invoke user queries from a search expression
From the search field: `S:"My query"`.
Can be combined with other filters such as `S:"My query" date:P3d` as long as the user queries do not contain `OR`.
A use-case is to have an RSS filter with a stable address or an external API call with the ability to update the user query.
* Draft of parenthesis logic
* More draft
* Working parenthesis (a OR b) (c OR d)
* Working (A) OR (B)
* Support nested parentheses + unit tests + documentation
* search:MySearch and S:3
* Refactor OPML export categories
Simplify code to comply with types hints.
And renamed a property to plural.
* Automatic simplification of layout for many feeds
New advanced property to automatically simplify the layout when there are many (1k+) feeds so that FreshRSS works out of the box with 20k+ feeds scenarios https://github.com/FreshRSS/FreshRSS/pull/4347
Merge https://github.com/FreshRSS/FreshRSS/pull/4356 first.
