Emit the task-tracking events
Based on initial patches by Mikolaj Konarski <email@example.com>
Use the new task tracing functions traceTaskCreate/Migrate/Delete.
There are two key places. One is for worker tasks which have a
relatively simple life cycle. Worker tasks are created and deleted by
the RTS. The other case is bound tasks which are either created by the
RTS, or appear as foreign C threads making calls into the RTS. For bound
threads we do the tracing in rts_lock/unlock, which actually covers both
threads coming in from outside, and also bound threads made by the RTS.