cwipc_view should get option to analyse pointcloud streams

[jackjansen]

Moved over from https://gitlab.com/VRTogether_EU/cwipc/cwipc_util/-/issues/59

It would be good if cwipc_view would analyse the pointcloud stream, and print some useful numbers at the end (where it already prints some statistics):

• first timestamp seen
• last timestamp seen
• delta-t of the timestamps seen
• guessed frame rate
• number of missed frames if the guessed frame rate is correct

With these, we could use cwipc_view --k4aoffline --nodisplay to check that our recordings are complete (so we wouldn't need the separate testing utility anymore).