Stacktrace in 'debug=1' format

Hi!

I'd like to propose a feature that allows to (optionally) dump a stack track in `debug=1` format. Currently agent hardcodes it to `debug=2`.

While `debug=2` format is probably more readable, `debug=1` has a rather large advantage - it includes `pprof` labels. This is especially handy when there are many goroutines doing similar work but handling different tasks/assignments/etc.

If there are no objections, I can probably prepare a PR. I think introducing a new command to preserve backward compatibility is the way to go here.