Modularize FileStoreTest and move to Gtest (#43383)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/43383
FileStore Test currently has a large blob of tests that throw
exceptions upon failure. This PR modularizes each test so they can run
independently, and migrates the framework to gtest.
ghstack-source-id: 111690831
Test Plan: Confirmed tests pass on devvm
Reviewed By: jiayisuse
Differential Revision: D22879473
fbshipit-source-id: 6fa5468e594a53c9a6b972757068dfc41645703e
