[PyTorch] Add corner case tests for IValue::use_count()
Pull Request resolved: https://github.com/pytorch/pytorch/pull/76418
There's some weird behavior currently with this accessor. Capture it in a test.
Differential Revision: [D31154949](https://our.internmc.facebook.com/intern/diff/D31154949/)
Approved by: https://github.com/ezyang
