Run all fallback kernels with FakeTensor (#88248)
This improves the memory compression of resnet18 from .84 -> .94 on inductor no-cudagraphs. It does mean that any extern kernel which incorrectly computes strides will be a hard error at runtime, but that's an issue we are going to have to face with dynamic shapes anyway. CC @ezyang, @SherlockNoMad
Pull Request resolved: https://github.com/pytorch/pytorch/pull/88248
Approved by: https://github.com/ezyang
