Added filtered search bar to issue boards

Added the filtered search bar onto the issue boards page. This does not add it into the issues modal, that will be done in a different merge request.

Tweaked the filtered search to allow for the search to be performed async like issue boards currently does. This means adding the updated parameter string into the issue boards store & then allowing the Vue code to react to it correctly. Also had to tweak this slightly to stop Droplab getting destroyed when pressing enter, instead it just stops propagation when handled async.

Tweaked the clear button as well so that when clicking it it now resets the filter & sends new AJAX requests to get the updated data.

Closes #28312 (closed)