This is a sub-task to WT-17914, dependent on WT-17943.

This is the fix command to calibrate the database size, fix the cluster's issue described in WT-17563.

What we need for this task is to make sure the size fix is safe at runtime, and the basic logic here is derived from the verify function of __wt_verify_disagg_database_size.

• The database size should always be the sum of all collections' latest checkpoint sizes.

The timing for inject this logic is in __checkpoint_update_disagg_database_size which will be called at the end of each checkpoint. As the command call is in different thread to checkpoint, we can introduce a state machine for signal sync across them, and use the util command of fetch_database_size or grafana dashboard for living check the result.