Code string API for fuser testing (#18884)
Summary:
This adds a C++ function `debugGetFusedKernelCode` as well as a Python binding `_jit_fuser_get_fused_kernel_code` that will, given a FusionGroup graph and a set of specified inputs, return the compiled kernel source code. We can then check the contents of this source code for verification of the fuser codegen backend.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/18884
Differential Revision: D14795508
Pulled By: jamesr66a
fbshipit-source-id: 8f6e9dd13ebbb517737d893b0b5f5e9aa06af124
