Profile with perf

For a first profiling :

• 1 TeV hadronic cascade with 30° inclination, N_showers = 100
• 1 TeV EM shower with 30° inclination, N_showers = 10
• 1 PeV hadronic cascade with 30° inclination, N_showers = 1

And for future profiling :

• add EM particle cuts at 0.5MeV (use case for radio)

Profile C8 core without the time-consuming modules :

• add --emcut 1e3 for a 1 TeV shower + add details to explain the flamegraphs and profiles