After SERVER-72489, the config server will always have a shardIdentity document. Initially it will use a fixed name of "catalogShard" but to simplify our system, it should use the "config" name, which is already used as the config server's shard id in places that require one, like two phase commit coordination and as the primary shard for the config and admin dbs.

There is also logic that special cases the config id to avoid failures from the config server not previously behaving like a normal shard, like not sending shard versions to it. The config server will now have all shard components, so we can remove those special cases, which is necessary to use "config" as the catalog shard's id.