Due to TIG-859, the hang analyzer may fail to attach and create core dumps in macOS tests. Core dumps are often the only way to get information about process state, and lack of them may completely block Server engineers on BFs, such as the recent BF-16858.
As a fallback measure, we should send SIGABRT to processes that the debugger has failed to create core dumps from. We have precedent from
SERVER-45342 of sending externally-created SIGABRTs and logging messages to distinguish them from internally-generated aborts. Since the signal handler is a separate thread that doesn't take locks, it should work in the case of a hang.