Experimental warning for named tensors (#26050)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/26050
Throws a warning once when someone attempts to attach names to a tensor.
This is guaranteed to happen at the callsite `set_named_tensor_meta`.
Test Plan: - run tests [namedtensor ci]
Differential Revision: D17331634
Pulled By: zou3519
fbshipit-source-id: 44f5e5c95acd9c7ba543c1210a3b1314aab348f0
