ddl: support the rolling upgrade. #6301
Merged
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We use this PR(#6274) as the dividing line to define whether it is a new version or an old version TiDB.
The old version TiDB initializes the column's offset and state here.
The new version TiDB doesn't initialize the column's offset and state, and it will do the initialization in run DDL function.
When we do the rolling upgrade the following may happen:
a new version TiDB builds the DDL job that doesn't be set the column's offset and state,
and the old version TiDB is the DDL owner, it doesn't get offset and state from the store. Then it will encounter errors.
This PR will fix it.