Primer export should allow the export of applications (filter by label)

Users want to export applications* from the OCP console UI. The first version allows the user currently only to export the complete project (=namespace), but a more fine granular export would be nice.

The topology shows workload and other resources grouped as application based on the app.kubernetes.io/part-of label.

To export all related resources to an application, the user should select one (maybe more later?) application names in the UI, that should create then an export resource with this label filter.

For example (just to get an idea, must not look exactly like this):

A matchLabels selector would only one app per export for now.

apiVersion: primer.gitops.io/v1alpha1
kind: Export
metadata:
  name: primer
spec:
  method: download
  user: kubeadmin
  selector:
    matchLabels:
      app.kubernetes.io/part-of: my-app

With a matchExpressions this might support also multiple apps, right?

apiVersion: primer.gitops.io/v1alpha1
kind: Export
metadata:
  name: primer
spec:
  method: download
  user: kubeadmin
  selector:
    matchExpressions:
      - {key: app.kubernetes.io/part-of, operator: In, values: [my-app1, my-app2]}