helm chart: support optional dnsConfig on deployment podspec

[stensonb]

Issue # (if applicable)

n/a

Reason for this change

i'd like the option of passing dnsConfig to the chart to control this value in the deployment's podspec.

Description of changes

helm templating, default value of empty.

Describe any new or updated permissions being added

none

Description of how you validated changes

helm template . shows no changes

sample from k8s docs : https://kubernetes.io/docs/concepts/services-networking/dns-pod-service/#pod-dns-config

helm template --set 'dnsConfig.options[0].name'=edns0 --set dnsConfig.searches='{ns1.svc.cluster-domain.example,my.dns.search.suffix}' . shows:

spec:
...
  template:
  ...
    spec:
    ...
      dnsConfig:
        options:
        - name: edns0
        searches:
        - ns1.svc.cluster-domain.example
        - my.dns.search.suffix
...

[cert-manager-prow]

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