[TXT Registry] Make the nonce stable when generating delete records

[Sewci0]

This PR addresses the issue of the current behavior being incompatible with Route53 when using TXT registry with encryption enabled. AWS requires the Delete change request to be called with the exact same record set that is currently present in Route53. However, this is not happening due to the following reasons:

1. The generateTXTRecord function generates both old and new format TXT records, each encrypted with a new random nonce.
2. The Records() function stores only one of these records in the labelsMap when iterating through the TXT labels.
3. The call to generateTXTRecord within Records() results in the deletion of the nonce from the labels.
4. The final call to generateTXTRecord within ApplyChanges regenerates the nonce again, leading to an entirely different target.

To resolve this issue, this PR disables the generation of old-style TXT records and old to new migrations when encryption is enabled. It also ensures that the txtEncryptionNonce does not get removed from labels, instead it is ignored when serializing.

Nonce generation has been moved outside of the EncryptText and the nonce get's added to the record's labels. This is required in order to ensure that the nonce exists on the record when it gets added to the cache.

Fixes: #3668
Supersedes: #3808

Checklist

• Unit tests updated

[k8s-ci-robot]

Hi @Sewci0. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[mloiseleur]

I'm unsure if and how the change in labels.go should be tested 🤔
Thanks for the test in registry.

/ok-to-test
/lgtm

[Sewci0]

/test pull-external-dns-lint

[Sewci0]

/retest

[mloiseleur]

/retest

[Sewci0]

/assign @njuettner

[mloiseleur]

/lgtm

[Sewci0]

/retest

[mloiseleur]

@Sewci0 If you commit --amend --no-edit and push, it should refresh the failed job.

[Sewci0]

@mloiseleur Thanks for looking into it, I had to do a few force pushes but it should be all good now.

[mloiseleur]

/lgtm
/assign @Raffo
/assign @johngmyers

[szuecs]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: szuecs

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