[Profiler] Use RAII wrapper to manage refcounts during python tracer startup. (#91646)
Refcounting is hard. (Citation needed.) https://github.com/pytorch/pytorch/pull/81242 introduced a corner case where we would over incref when breaking out due to max (128) depth. https://github.com/pytorch/pytorch/pull/85847 ostensibly fixed a segfault, but in actuality was over incref-ing because PyEval_GetFrame returns a borrowed reference while `PyFrame_GetBack` returns a strong reference.
Instead of squinting really hard at the loops, it's much better to use the RAII wrapper and do the right thing by default.
I noticed the over incref issue because of a memory leak where Tensors captured by the closure of a function would be kept alive by zombie frames.
Differential Revision: [D42184394](https://our.internmc.facebook.com/intern/diff/D42184394/)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/91646
Approved by: https://github.com/albanD
