Make GenLazyNativeFuncDefinition generator to be customizable in lazy codegen (#87823)
As part of the ongoing LTC migration effort, PyTorch/XLA is updating its codegen to use `xla::Shape` instead of `torch::lazy::Shape`. To achieve this, this PR updates the codegen to make the `GenLazyNativeFuncDefinition` generator customizable.
The existing `GenLazyNativeFuncDefinition` is kept by using the initial default values, so this change should not introduce any new behaviors to the existing codegen in PyTorch.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/87823
Approved by: https://github.com/alanwaketan, https://github.com/wconstab
