Cron String: Clean up.

[davinchia]

Tell us about the problem you're trying to solve

Last part of #2170 . Follow up to #11431 .

Clean up work:

• Write a db migration to migrate any rows in the connection table with the old manual column set and the old schedule format that do not have the new scheduleType column set to the new schema. After that, drop the old manual column. This migrates all the previous connections schedules to the new format.
• Remove all backward compatible code in the persistance layer, the server and the temporal workflow.

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Describe the alternative you’ve considered or used

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Additional context

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Are you willing to submit a PR?

Remove this with your answer :-)

[mfsiega-airbyte]

Note: in the scope of this task, let's ensure that we have validation where it's warranted around sending sane scheduling info (e.g., schedule type matches schedule data should be validated in the api and in the persistence layer).

[mfsiega-airbyte]

Note: revisit e2e test cases before closing this out.

[mfsiega-airbyte]

Note: consider if there's any code duplication to be cleaned up (e.g., https://github.com/airbytehq/airbyte/pull/16690).