trace_start - start collecting driver trace

void trace_start(filename, auto_stop_sec = 30)

Call this funciton to start collecting tracing information, this include LPC
funciton level execution information.

Driver will stop collection and dump to `filename` on `trace_end()`, or
after `auto_stop_sec` seconds, default to be 30.

Note: do not leave tracing enabled for too long, otherwise you will run out of
memory.

trace_end()