feat(service): allow using target annotation

[GMartinez-Sisti]

Description

From closed #2833 (thanks @eburghar!).

This pull request add the possibility to override the target of service the way we can do with ingress. It allows for example to publish an IP for a service when the load balancer is natted.

apiVersion: v1
kind: Service
metadata:
  annotations:
    external-dns.alpha.kubernetes.io/hostname: imap.example.com,pop3.example.com,smtp.example.com
    external-dns.alpha.kubernetes.io/target: X.X.X.X
spec:
  ports:
    - port: 25
      name: smtp
    - port: 143
      name: imap
    - port: 110
      name: imap
  selector:
    app: mail
  type: LoadBalancer

Fixes #2240

Checklist

• Unit tests updated
• End user documentation updated

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[johngmyers]

Please add a AAAA test,

[GMartinez-Sisti]

Please add a AAAA test,

Done.

[szuecs]

/ok-to-test

[johngmyers]

/lgtm

[szuecs]

/approve

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: GMartinez-Sisti, szuecs

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