test(dns): Verify DNS Endpoint Provider aggregation logic

[fabikova]

Description

This PR implements the test scenarios defined in issue #811 to verify the new DNS Endpoint Provider functionality.

It validates the aggregation workflow where multiple "Source" DNSRecords (acting as endpoint feeders) merge their endpoints into a single central "Destination" DNSRecord (acting as a Zone), which then propagates the records to an upstream provider (e.g., AWS).

Scenarios covered:

1. Creation of a Destination DNSRecord pointing to a real provider (AWS) with the required zone label.
2. Creation of multiple Source DNSRecords pointing to the endpoint provider.
3. Verification that source endpoints are correctly merged into the destination record by the operator.
4. Verification that the merged records are successfully resolved via external DNS.

Closes #811

Changes

• New Test: Added testsuite/tests/singlecluster/gateway/dnspolicy/dns_records/test_dns_endpoint_provider.py which implements the test cases specified in the issue.
• Helper Methods: Updated DNSRecord class in testsuite/kuadrant/policy/dns.py with:
  • wait_for_endpoints_merged
  • wait_until_resolves