Implement a Selector component to list multiple entries without the search limitation

[carma12]

It would be good to have a separate user selector component which would be reusable on other places and would contain more logic.

E.g. this select that is using useGetActiveUsersQuery will not work if somebody will want to select a user which is not part of the first 100 users (resp. search limit) returned by the query. If you check the old UI, you will see that is has search capabilities which overcomes this limitation.

The selector would also simplify this dialog. Implementing it is beyond scope of this PR, thus takes this feedback as highlight of an issue.

Originally posted by @pvoborni in #219 (comment)