Add file-line info for jit.load and string frontend (#21217)
Summary:
This makes file-line reporting also work for things loaded using `torch.jit.load()` as well as the string frontend (via `CompilationUnit`)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/21217
Differential Revision: D15590838
Pulled By: jamesr66a
fbshipit-source-id: 6b6a12574bf9eca0b83f24f0b50535fda5863243
