Change TCPStore world_size and is_master to be optional (#51809)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/51809
Changes to TCPStore which will make world_size and is_master optional parameters for initialization.
API before change:
```python
# arguments: host_name, port, world_size, is_master, timeout=300s
server_store = dist.TCPStore("127.0.0.1", 0, 2, True)
client_store = dist.TCPStore("127.0.0.1", 0, 2, False)
```
API after change:
```python
# arguments: host_name, port, world_size=-1, is_master=False, timeout=300s
server_store = dist.TCPStore("127.0.0.1", 0, is_master=True)
client_store = dist.TCPStore("127.0.0.1", 0)
```
Test Plan: Imported from OSS
Reviewed By: heitorschueroff
Differential Revision: D26461770
Pulled By: H-Huang
fbshipit-source-id: 5b2157029c73e8706e158cd49ecce60c9f3a7f41
