torch/csrc/profiler/README.md - stubs, RecordFunction, Autograd interaction (#108470)
Technical details about the profiler - stubs for the stuff I haven't had time to fill out yet, plus details about RecordFunction and the profiler's interaction with autograd.
reviewers - see https://github.com/pytorch/pytorch/blob/06c41eea9e37b5799e4f14601c95fa7810297759/torch/csrc/profiler/README.md for rendered markdown
Pull Request resolved: https://github.com/pytorch/pytorch/pull/108470
Approved by: https://github.com/aaronenyeshi
