Add summary at the end of execution process

[AndreyNikiforov]

To improve end-user experience, we need to print summary of:

• actions performed
• bandwidth used
• space on disk used or released
• overall time spend processing

Caveats: summary should not include authentication, only actual processing

[AndreyNikiforov]

@jkcchan let brainstorm here on what, when, and why we want to show to icloudpd users. We can discuss "how" in PR or here.

I can think of two user profiles: ad-hoc runners and watchers (with --watch-with-interval or any other way to kick icloudpd periodically).

I remember a number of asks to improve performance/download speed, so addressing concerns of bottlenecks may be one of the "why"s (for ah-hoc users primerely).

Those that focus on reliable synchronization of assets (and watching for changes) are probably more interested in a metric highlight their focus area, e.g. "delay between asset creation in icloud and its appearance in local storage".

WDYT?