enhance ReplaceRRSet to track owner UID and generation for accurate record set management

[fr6nco]

Summary

Fix stale PowerDNS RRSet reuse when a Kubernetes DNSRecordSet is deleted and recreated with the same generation.

Previously, the PowerDNS sync logic only checked the stored OBSERVED_GENERATION comment and ignored object identity. If a record was deleted and recreated immediately, the new object could have the same generation as the old one but a different UID, and PowerDNS would incorrectly treat the RRSet as already current.

This patch stores the Kubernetes object UID in PDNS comments and treats an RRSet as current only when both generation and UID match. Legacy records that only have generation metadata are treated as stale and reconciled on the next pass.

Impact

• prevents stale RRSet reuse after delete/recreate cycles
• supports migration for existing records created before UID tracking existed
• preserves correct cleanup/delete behavior for stale and deleted objects

Contiation of #82