add a new FunctionSchema kind called scratch
Pull Request resolved: https://github.com/pytorch/pytorch/pull/79659
The scratch op expose intermetidate/scratch tensors used in kernel implementation
as kernel input arguments so a memory planning algorithm can plan memory for those
tensors.
Differential Revision: [D37194429](https://our.internmc.facebook.com/intern/diff/D37194429/)
Approved by: https://github.com/bdhirsh
