Discussed in D11057, but we want to "freeze" the previous implementation of `createUpdateDBOpsForThreadStoreThreadInfos` in place to support old migrations while re-introducing a new version that only handles "MinimallyEncoded -> MinimallyEncoded` migrations. We only have "MinimallyEncoded -> MinimallyEncoded` migrations in the future, so IMO it doesn't make sense to clutter up `createUpdateDBOpsForThreadStoreThreadInfos` to be able to handle
- LegacyRawThreadInfos => LegacyRawThreadInfos
- LegacyRawThreadInfos => MinimallyEncodedRawThreadInfos
- MinimallyEncodedRawThreadInfos => MinimallyEncodedRawThreadInfos
It also lets us avoid having to go back and test some of the old migrations when we tweak `createUpdateDBOpsForThreadStoreThreadInfos`.
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Depends on D11057