Pytest frame trimming is over deleting frames

[lucamuscat]

In order to prettify the final output, Perfsephone indiscriminately ignores all pytest related frames, assuming that pytest related frames will only show up outside of the test being profiled itself.

It would be nice if the trimmed pytest frames are actually those frames outside of the test, and not pytest related frames inside the test. There are definitely code bases (namely, this one), which uses pytest itself INSIDE their own tests for whatever reason.