Move existing target determinator to tools (#63809)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/63809
This moves out the modulefinder determinator to `tools/testing` since it is supposed to be CI-only. This also simplifies run_test.py a little bit.
Test Plan: Imported from OSS
Reviewed By: malfet, seemethere, janeyx99
Differential Revision: D30497438
Pulled By: driazati
fbshipit-source-id: 1d203037af5af6a20c1e7812da935e7cbb5cd82f
