While looking for a solution to #3088, I realize we need a new hook that signals a test item has finished executing.

Without this hook one needs to implement pytest_runtest_logreport and juggle around the various setup, call and teardown reports to infer when a test item has finished running, which is downright problematic as pytest-dev/pytest-xdist#218 shows: there I had to implement a new "event" to signal that a test has been complete, which besides fixing a bug also allows pytest-rerunfailures to work with xdist.