apps: cert-manager networkpolicies with generator

[aarnq]

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What kind of PR is this?

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• kind/feature
• kind/improvement
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What does this PR do / why do we need this PR?

Use networkpolicy generator for cert-manager.

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Checklist

• Proper commit message prefix on all commits
• Change checks:
  • The change is transparent
  • The change is disruptive
  • The change requires no migration steps
  • The change requires migration steps
• Metrics checks:
  • The metrics are still exposed and present in Grafana after the change
  • The metrics names didn't change (Grafana dashboards and Prometheus alerts are not affected)
  • The metrics names did change (Grafana dashboards and Prometheus alerts were fixed)
• Logs checks:
  • The logs do not show any errors after the change
• Network Policy checks:
  • Any changed pod is covered by Network Policies
  • The change does not cause any dropped packages in the NetworkPolicy Dashboard
• Pod Security Policy checks:
  • Any changed pod is covered by Pod Security Admission
  • Any changed pod is covered by Gatekeeper Pod Security Policies
  • The change does not cause any pods to be blocked by Pod Security Admission or Policies
• Falco checks:
  • The change does not cause any alerts to be generated by Falco
• Audit checks:
  • The change does not cause any unnecessary Kubernetes audit events
  • The change requires changes to Kubernetes audit policy
• Bug checks:
  • The bug fix is covered by regression tests