Update `DBCheckpointStorage` to save to the new checkpoint tables.
Currently, a new temp table has been added which has kept the existing checkpoints table alongside the new ones. As part of this change, the liquibase schema's should be updated to drop the original checkpoint table and recreate it with the new main checkpoint table structure (the name of the new table should be set to the same name of the existing table).
Fields that cannot be populated yet should either be filled with `null` or just filled with dummy data. These will be filled in properly in future tasks.
This task includes saving flowState into the appropriate column and the rest of the fields in the Checkpoint class (that do not have their own fields) into checkpoint_value.
The functionality of the checkpoints should not change at this point. Data is simply being saved in slightly different ways.