[agent-operator] add kustomization to access directory and crds from within kustomize

[wibed]

is this viable? id like to use something along those lines:

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization

resources:
  - https://github.com/grafana/agent/tree/main/production/operator/crds

or

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization

resources:
  - https://github.com/grafana/helm-charts/charts/agent-operator/crds

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