feat(service): optionally create DNS entry for each pod

[redbaron]

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Description

headless service already supported mode where DNS entry is created for each pod when spec.hostName is present. Not all controllers populate that field, but it is sometimes desireable to create DNS entry per pod nevertheless.

This commit adds new annotation service-pod-endpoints , which when set on a headless service makes external-dns to create endpoint per pod using pod name as a prefix.

Checklist

• [x] Unit tests updated
• [x] End user documentation updated