add migration utilities

[awaelchli]

What does this PR do?

Adds migration functions. When a checkpoint gets loaded, we migrate it automatically.

Fixes #9396

Does your PR introduce any breaking changes? If yes, please list them.

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[awaelchli]

Closing, there is too little value for this atm and the effort is quite large.

[carmocca]

Do you want to close the linked issue too? Or just dropping this implementation?

[awaelchli]

The linked issue can be kept open for the community if we want.