Add support for Kubernetes namespace selection

[tliron]

The UI currently tracks related CRs (e.g. Repository) in the "default" namespace only.

Ideally there would be a dropdown to select an individual namespace or all namespaces.

[ChristopherFry]

The UI currently tracks related CRs (e.g. Repository) in the "default" namespace only.

Confirming the Config as Data UI does support looking for resources in a namespace other than "default" today. The UI looks for resources as defined by the resourcesNamespace value in the app-config.yaml file as defined by the Configuration as Data Backend Plugin.

This value can be updated by either updating the value directly in the app-config.yaml, extending the app configuration with another configuration file overriding any values as needed (this is the pattern that Nephio follows), or setting the APP_CONFIG_configAsData_resourcesNamespace environment variable using environment variable overrides.

Ideally there would be a dropdown to select an individual namespace or all namespaces.

I can look into adding this. Although the UI does support looking for resources in another namespace, the namespace does need to be defined upfront.