[bitnami/nginx] Allowing for customize dnsPolicy and dnsConfig for nginx

[sepauli]

Description of the change

This PR adds options to configure dnsPolicy and dnsConfig for the nginx chart.

Benefits

It would allow users to fine-grain their DNS resolution process, especially useful in an intranet environment.
This is an example:

dnsPolicy: "None"
dnsConfig:
  nameservers:
    - 192.0.2.1 # this is an example
  searches:
    - ns1.svc.cluster-domain.example
    - my.dns.search.suffix
  options:
    - name: ndots
      value: "2"
    - name: edns0

/usr/bin/helm template -f settings.yaml ./nginx | grep dnsPolicy -A 10                                                                              ✔ 
      dnsPolicy: None
      dnsConfig:
        nameservers:
        - 192.0.2.1
        options:
        - name: ndots
          value: "2"
        - name: edns0
        searches:
        - ns1.svc.cluster-domain.example
        - my.dns.search.suffix

Possible drawbacks

N/A

Applicable issues

• fixes [bitnami/nginx] Allowing for customize dnsPolicy and dnsConfig for nginx #26612

Additional information

Checklist

• Chart version bumped in Chart.yaml according to semver. This is not necessary when the changes only affect README.md files.
• Variables are documented in the values.yaml and added to the README.md using readme-generator-for-helm
• Title of the pull request follows this pattern [bitnami/<name_of_the_chart>] Descriptive title
• All commits signed off and in agreement of Developer Certificate of Origin (DCO)