Statistics on imaging steps

[TallFurryMan]

Make the Scheduler consolidate statistics on each step of the observation session:

• Tracking/slewing duration and speed (time vs. angular distance)
• Alignment performance
• Focus performance
• Guiding calibration performance
• Capture effective duration

Statistics must store constraints used in each tab to be relevant in comparisons.

These statistics will be useful for a number of features, setup comparisons and for retrospective on past observations.

This feature can start with basic log file entries, and evolve into a separate tab.

[TallFurryMan]

https://invent.kde.org/education/kstars/-/issues/28