pytorch

58444387 - [sharded_tensor] add default fields to ShardedTensorMetadata (#62867)

[sharded_tensor] add default fields to ShardedTensorMetadata (#62867) Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/62867 This add default fields for ShardedTensorMetadata, to allow easy construction and modification afterwards. ghstack-source-id: 135284133 Test Plan: ShardedTensorMetadata validity should be guarded with `init_from_local_shards` API and its tests. Reviewed By: pritamdamania87 Differential Revision: D30148481 fbshipit-source-id: 0d99f41f23dbeb4201a36109556ba23b9a6c6fb1