Add tests for the dns endpoint provider

[averevki]

Summary

Add a new provider implementation (endpoints) that allows any resource that fulfils the contract for an external-dns Endpoint resource to act as a central "zone" resource that can be updated by many other endpoint resources

Documentation

Endpoint provider: Kuadrant/dns-operator#469
PR: Kuadrant/dns-operator#504

Test cases

1. Create endpoint provider secret with GVR and label.
2. Create destination dnsrecord pointing to the DNS provider (aws, gcp or azure).
3. Create 2 dnsrecords with unique subdomains and different IPs. DNSRecords should have endpoint provider label on them.
4. Verify that records are accessible.