[TXT Registry] Disable generation of old style txt records when encryption is enabled

[Sewci0]

As mentioned in the issue, current behaviour is unable to work with AWS which requires the Delete change request to be called with the exact same record set that is currently present in Route53. This is currently not happening due to:

1. generateTXTRecord generates both the old and new format txt records. Each record ends up being encrypted with new random nonce.
2. Records() will only store one these in the labelsMap when iterating through the TXT labels.
3. Call to generateTXTRecord within Records() will delete the nonce from the labels.
4. Final call to generateTXTRecord from within ApplyChanges will have to regenerate the nonce once again, ending up with an entirely different target.

This change disables the generation of the old style txt records and old to new migrations when encryption is enabled.

Fixes #3668
Depends on #3724

Checklist

• Unit tests updated

[k8s-ci-robot]

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[k8s-ci-robot]

PR needs rebase.

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[Sewci0]

Superseded by: #3901