run_test.py: add option to run only core tests (#63976)
Summary:
This is in response to a feature request from some folks in the core team to have a local command that would only run relevant "core" tests. The idea is to have a local smoke test option for developers to run locally before making a PR in order to verify their changes did not break core functionality. These smoke tests are not targeted to be short but rather relevant.
This PR enables that by allowing developers to run `python test/run_test.py --core` or `python test/run_test.py -core` in order to run the CORE_TEST_LIST, which is currently test_nn.py, test_torch.py, and test_ops.py.
I am not the best person to judge what should be considered "core", so please comment which tests should be included and/or excluded from the CORE_TEST_LIST!
Pull Request resolved: https://github.com/pytorch/pytorch/pull/63976
Test Plan:
```
(pytorch) janeyx@janeyx-mbp test % python run_test.py --core -v
Selected tests: test_nn, test_ops, test_torch
Running test_nn ... [2021-08-25 14:48:28.865078]
Executing ['/Users/janeyx/miniconda3/envs/pytorch/bin/python', 'test_nn.py', '-v'] ... [2021-08-25 14:48:28.865123]
test_to (__main__.PackedSequenceTest) ... ok
test_to_memory_format (__main__.PackedSequenceTest) ... ok
```
Reviewed By: walterddr
Differential Revision: D30575560
Pulled By: janeyx99
fbshipit-source-id: 3f151982c1e315e50e60cb0d818adaea34556a04
