[Feature] Enable configurable "mandatory" filters

Background: we have k8s clusters which as on average 3K active alerts per cluster.

I would like to pervent users from being abile to load all the alerts - bad for both user experience and server loading.

Idea: as admin, be able to define some filters such as "namespace", "cluster" as mandatory, which users must select (via UI or via query string) in order to use karma UI.