Move all event time recording to `CallTimes`
Move all event time recording to `CallTimes`

Pulls time stamp collection out of the core event loop/handlers and
into this built-in app's callbacks.

- record data points for calls which do not necessarily connect
  and/or contain > 1 leg.
- store hangup causes for each call
- add a new `call_types` metric which provides float "annotations"
  for depicting which causes / apps correspond to each data point
- clip call rates at 1k (we get it sofia is super bursty)

sangoma/switchy