By passing a config and not a Arc'ed LeaderScheduler, callers need to use `Bank::leader_scheduler` to access the scheduler. By using the new constructor, there should be no incentive to reach into the bank for that object.
By passing a config and not a Arc'ed LeaderScheduler, callers need to use `Bank::leader_scheduler` to access the scheduler. By using the new constructor, there should be no incentive to reach into the bank for that object.