[Distributed] Adding Python tests for the TCPStore getNumKeys and deleteKey (#45402)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/45402
Previous diffs in this stack implemented the getNumKeys and deleteKey
APIs in the c10d Store as well as added tests at the C++ layer. This diff adds
tests at the Python level in test_c10d.py
ghstack-source-id: 112997161
Test Plan: Running these new python tests as well as previous C++ tests
Reviewed By: mrshenli
Differential Revision: D23955729
fbshipit-source-id: c7e0af7c884de2d488320e2a1d94aec801a782e5
