[Feature] display latency should be done by default

[egobillot]

Is your feature request related to a problem? Please describe.
I think users want by default the average latency per function. So we should remove the flag -l for latency and make it the default behaviour

Describe the solution you'd like
calltop.py will display latency metrics.
calltop.py --no-latency won't display latency metrics

Describe alternatives you've considered
Do we need the --no-latency flags ? the only reason to keep it, is for performance, as we need a second eBPF attached on return.