Use linecache.lazycache to cache generated code. (#63453)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/63453
Instead of patching linecache.getlines, use linecache.lazycache and
parts of the loader protocol described in PEP-302
Test Plan:
python3 test/test_fx.py
Imported from OSS
Reviewed By: suo
Differential Revision: D30388176
fbshipit-source-id: 92933711ecf3a21a07e1d6b0d1185ab0efd8341c
