* Rework sampling trace counter names + new trace counters
- reformulate trace counter names for easier comparison (thread sampling)
- new process-level trace counters for context switches (thread sampling)
- new process-level trace counters for page faults (thread sampling)
- new process-level trace counters for CPU time (thread sampling)
- new thread-level trace counters for context switches (sampling)
- new thread-level trace counters for page faults (sampling)
* tweak header include in backtrace.cpp