Add manual meta implementations to quantize_per_tensor.tensor and co (#89958)
When you are writing a meta function, you cannot call item() on the tensor because there is no real data on the tensor and it will fail. The error message was not very good in this case, see also https://github.com/pytorch/pytorch/issues/89959
This PR takes a brute force approach to resolving the problem: just manually define meta implementations for the naughty functions that are calling item(). However, this results in a lot of code duplication. The easiest way to avoid this situation is to rewrite the decomps so they don't call item. It should not be that difficult to use direct tensors on your operations, as scalar tensors can broadcast too.
I could only test this with `buck test @mode/opt -c python.package_style=inplace //executorch/backends/test:test_backends` in internal with D41555454. Test coverage needs to be improved, otherwise don't blame us when we break you.
Signed-off-by: Edward Z. Yang <ezyang@fb.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/89958
Approved by: https://github.com/jerryzh168
