[2/n] [c10d] Introduce the 'multiTenant' constructor parameter in TCPStore (#58329)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/58329
This PR is part of a stack that addresses the GitHub issue #41614; it introduces:
- A new `multiTenant` constructor option for the `TCPStore` class indicating whether multiple store instances can be initialized with the same host:port pair.
- Updates to the C10d distributed (elastic) rendezvous and the `init_process_group` method to leverage the new `multiTenant` feature.
Note that the multi-tenancy feature itself is implemented in the fourth PR of this stack. In this PR passing `true` to `multiTenant` results only with a warning output.
ghstack-source-id: 130676389
Test Plan: Run the existing tests since there are no behavioral changes.
Reviewed By: rohan-varma
Differential Revision: D28424978
fbshipit-source-id: fb1d1d81b8b5884cc5b54486700a8182a69c1f29
