execution stats for all modules

[ekuleshov]

Commands like flutter pub run build_runner build print some execution stats at the end:

[INFO] Succeeded after 39ms with 0 outputs (0 actions)

It will be convenient to see some similar execution times when you run mono_repo pub run build_runner build and such. It already reports progress, so the times could be shown right next to succeeded counts.

Successes: 4
Remaining: 1