Moves jit shape function registration to python. Like jit decompositions, a script must be run after adding new definitions which serializes them in a c++ file.
This was a request so that torch-mlir could define functions in python and upstream their shape functions. cc @silvasean @makslevental
Pull Request resolved: https://github.com/pytorch/pytorch/pull/75546
Approved by: https://github.com/davidberard98
