Allow per-namespace annotations-risk-level

[sathieu]

Raising annotations-risk-level to High is good, but we need a way to add exceptions for specific namespaces that we now are using safe parameters.

For example, we use this for MinIO:

      nginx.ingress.kubernetes.io/configuration-snippet: |
          chunked_transfer_encoding off;

Proposed change: add a new option in ConfigMap annotations-risk-level-excluded-namespaces containing a space-separed list of namespaces where annotations-risk-level is set to Critical.

[k8s-ci-robot]

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[sathieu]

Other usecases (for kube-apiserver):

    nginx.ingress.kubernetes.io/server-snippet: |
      client_header_buffer_size 40k;
      large_client_header_buffers 4 40k;