FIX: register customOptions as select kit filter (PR #14933)

We are allowing plugins to define custom filters which are added to CUSTOM_USER_SEARCH_OPTIONS const. However, we need to have static placeholder for custom filters, so those props will be passed, and we can use it later.


What do you think of naming it customSearchOptions instead?

Doesn’t this mean every instance of the component gets the same object instance? That’s probably not what we want.