Stacktrace in 'debug=1' format

[pborzenkov]

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.