Resolve follow-up from "Fetch projects and subgroups in async on group audit event destinations page"

What does this MR do and why?

This MR addresses multiple minor issues in filter implementation. See Follow-up from "Fetch projects and subgroups in... (#439506 - closed) for details

MR acceptance checklist

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Screenshots or screen recordings

How to set up and validate locally

• Open Secure -> Audit Events -> Streams -> HTTP Observe "Filter by groups/projects" dropdown behavior

Note: if you want to observe loading behavior it is better to create some "very slow network profile" (even slow 3g was too fast for me) in gdk

Related to #439506 (closed)