[Profiler] Memory profiler part 1: Gradient identification (#86802)
There are multiple ways to indentify that a Tensor is a gradient. (A subset of which also give additional context.) So to start off I've made a utility to handle that determination.
Differential Revision: [D39920730](https://our.internmc.facebook.com/intern/diff/D39920730/)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/86802
Approved by: https://github.com/chaekit
