The Sharding Routing Info Stability DistLock doesn't offer the assumed protection

We added the Sharding Info Stability DistLock with the idea that it was going to serve as a barrier between DDL operations which use the old vs new metadata format. However, it doesn't actually provide the assumed protection, because even though two different shards could hold it, the first one to release it will release it for everyone.

Because of this we should remove it and implement a proper protection mechanism based on 2-Phase FCV or something similar.