fix(kube): cleanup config manifests

[nourspace]

• Use patches instead of deprecated patchesStrategicMerge
• Remove hardcoded namespace from resources This is automatically added by the config kustomization. Having it requires overlays to specify namespace: system or others in their patches: target which is confusing.

Tests

Created a dummy config kustomization and tested that allow following scenarios result in the same kustomize build

• Specifying the namespace: example-ns
• Removing the namespace (results in exactly the same manifests, but with cosmos-operator-system as namespace ofc)
• Removing the target from the patch

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

namespace: example-ns

resources:
  - /path/to/cosmos-operator/config/default

patches:
  - target:
     kind: Deployment
     name: controller-manager
    patch: |-
      apiVersion: apps/v1
      kind: Deployment
      metadata:
        name: controller-manager
      spec:
        template:
          spec:
            containers:
            - name: manager
              resources:
                limits:
                  memory: 128Mi