Should return error if the specified resharding operation does not exist or has completed already.
Should enter the critical section of the resharding operation if not already reached.
Should durably record decision to commit the resharding operation if not already done.
The commit flow is already implemented for resharding. This ticket is about introducing a new promise/future pair that the ReshardingCoordianator waits on and is fulfilled by the commitReshardCollection command.
We should consider adding a server parameter to preserve the existing "reshardin commits as quickly as possible" style of behavior to avoid impacting existing tests.