[1/n] Update testing lib*.so path (#61960)
Summary:
### Issue
Build PyTorch wheel packages during build stage for pull requests and install during test stage.
### Fix
Update all tests which call lib*.so (under `./build folder`), change to call lib*.so in `{ent}/pytorch/lib/python3.8/site-packages/torch`
### Diff
This diff starts to update test_fx, test_backend and test_torchbind first to check if current ci pass
Pull Request resolved: https://github.com/pytorch/pytorch/pull/61960
Test Plan: check of all ci workflows pass
Reviewed By: malfet, saketh-are
Differential Revision: D29823235
Pulled By: tktrungna
fbshipit-source-id: e7f652def698e303d4843fbaedf4859f5eca2fd9
