Improve stack trie suffix pruning

[ezyang]

I'm still regularly seeing stack tries that look like this:

torch/nn/modules/module.py:1566 in _wrapped_call_impl
torch/nn/modules/module.py:1575 in _call_impl
torch/_dynamo/eval_frame.py:433 in _fn
torch/nn/modules/module.py:1566 in _wrapped_call_impl
torch/nn/modules/module.py:1575 in _call_impl
torch/_dynamo/convert_frame.py:1116 in __call__
[[2/0]](https://interncache-all.fbcdn.net/manifold/tlparse_reports/tree/logs/.tmp0umcnJ/index.html#[2/0]) [[2/1]](https://interncache-all.fbcdn.net/manifold/tlparse_reports/tree/logs/.tmp0umcnJ/index.html#[2/1]) torch/_dynamo/convert_frame.py:472 in __call__

The torch/_dynamo/convert_frame.py:1116 in __call__ definitely need to be killed. But there's also some funny business with _wrapped_call_impl indirection that also is unnecessary 🤔