Allow for inverted namespace selection in loki.source.kubernetes_events

[thelooter]

Request

The namespace field in the loki.source.kubernetes_events should allow to specify a list of namespaces to exclude, e.g. by prefixing them with an exclamation mark.

Use case

This would allow to have a global alloy deployment which collects everything that doesn't need a special configuration, while still allowing the user to create special configurations for specific namespaces. If a user wanted to currently use this field for that purpose, the use would need to provide an exhaustive list in the main deployment, which isn't always feasible