Allow specifiying inputs as GradientEdge in autograd APIs (#110867)
This can be useful for advanced users (like AOTAutograd) who don't want to keep the corresponding Tensor alive (for memory reasons for example) or when inplace op will change the Tensor's grad_fn (but gradients wrt to the original value is needed).
I went minimal API change but open to suggestions.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/110867
Approved by: https://github.com/soulitzer
