torch.Assert: make it torch.jit.script'able (#47399)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/47399
Currently torch.Assert is not scriptable, which makes it not very useful for production code. According to jamesr66a , moving this to c++ op land will help with scriptability. This PR implements the change.
Note: with the current code the Assert is scriptable but the Assert is a no-op after being scripted. Would love suggestions on how to address that (can be in future PR).
Test Plan:
```
python test/test_utils.py TestAssert.test_assert_scriptable
python test/test_utils.py TestAssert.test_assert_true
python test/test_fx.py TestFX.test_symbolic_trace_assert
```
Imported from OSS
Reviewed By: eellison
Differential Revision: D24740727
fbshipit-source-id: c7888e769c921408a3020ca8332f4dae33f2bc0e
