Ensure history update_time is set when exporting

[davelopez]

Addresses #18068 (comment)

The default is now so we should always have a value in the Python model even if the column can be nullable.
561e6e9 opened a can of worms... so falling back to a simple fix. At this point, we can be sure the history update_time will never be None.

How to test the changes?

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• This is a refactoring of components with existing test coverage.
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[jdavcs]

Thank you, @davelopez!