Job to cleanup "old" TXTs

[maksymvavilov]

What

We changed the format of our TXTs. In order to do migration, we enabled the controller to read old ones and translate metadata into new records.
This creates a potentially problematic configuration in the provider.
We need a "job" to run against a provider and remove old records.

How

We can read creds from provider secrets that are referenced by DNS Records.
The new format of the records is prefix-hash-recordType-host; the old format is prefix-recordType-host. This can be used to pattern match and nuke old records. To safeguard deletion, new records will have version=1 in the target.

[philbrookes]

it might be worth having a test that the new version of the record exists before deleting the old one.

[azgabur]

After this is implemented I will check with an upgrade test.