Add tests for PyTorch operators

[ScottTodd]

Could look at the Python test cases in https://github.com/pytorch/pytorch/tree/main/test, or lean more on tests in torch-mlir: https://github.com/llvm/torch-mlir/tree/main/test. There are also some tests in https://github.com/nod-ai/SHARK-TestSuite/tree/main/e2eshark/pytorch/operators.

Generally looking for proof that the work tracked in nod-ai/SHARK-ModelDev#347 has fully landed in IREE and is supported across the full range of targets.