Block dns provider secret deletion when it's still referenced by a DNSRecord

[mikenairn]

This has been discussed before, and the current approach is to put it on the user to make sure all DNSRecords referencing a dns provider secret are deleted first. This isn't a great experience, especially during testing.

This ticket is to look into alternative options, if there are any, to allow the secret to remain in place while still being referenced by any existing DNSRecord.

Related:

• https://github.com/Kuadrant/testsuite/pull/615/files#r1914395188
• DNSRecord CR gets stuck in deletion when whole namespace is being deleted #267
• harden DNSRecord clean up when namespaces deleted #106

[maleck13]

The main issue I see is if the secret is referenced by more than one policy / record. Do we need a refernce count. IE how many records reference this secret and then if the ref count hits 0 remove the finalizer?