remove symbolic variable part 1 (#17986)
Summary:
As discussed with gchanan we should deduplicate symbolic_variable and symbolic_script to prepare for the future merge with derivatives.yaml.
This PR moves most easy formulas to symbolic_script.
TODO: run benchmarks to make sure no perf regression
cc: apaszke zdevito wanchaol
Pull Request resolved: https://github.com/pytorch/pytorch/pull/17986
Differential Revision: D14766412
Pulled By: ailzhang
fbshipit-source-id: d95a3f876e256c0f505779a71587c985571d3b8f
