1. Moving the _create_config and create_config functions from build_fuzzers_test.py and run_fuzzers_test.py into test_helpers.py (which is now part of cifuzz instead of infra) and share code between them.
2. Rename artifacts_dir to crashes_dir in run_fuzzers.py. "artifacts" is ambiguous.
3. Make some small changes to pytest.ini to improve debugging.
1. Use pyfakefs when possible instead of tempdir
2. Favor decorators instead of contextmanagers when mocking for less indentation and greater consistency.
Abstract away OSS-Fuzz specific bits into the OSSFuzz implementation
of the ClusterFuzzDeployment class. This will make it easier to implement
support for other deployments of ClusterFuzz (including ClusterFuzzLite).
jonathanmetzman