Refactor torch.*solve tests (#25733)
Summary:
Changelog:
- De-duplicate the code in tests for torch.solve, torch.cholesky_solve, torch.triangular_solve
- Skip tests explicitly if requirements aren't met for e.g., if NumPy / SciPy aren't available in the environment
- Add generic helpers for these tests in test/common_utils.py
Pull Request resolved: https://github.com/pytorch/pytorch/pull/25733
Test Plan:
- All tests should pass to confirm that the change is not erroneous
Clears one point specified in the discussion in https://github.com/pytorch/pytorch/issues/24333.
Differential Revision: D17315330
Pulled By: zou3519
fbshipit-source-id: c72a793e89af7e2cdb163521816d56747fd70a0e
