* Tweaks tresholds for logging high forwarding latency/jitter.

Previous attempt showed skewed jitter (i. e. more than 10x latency),
But, no large latency.

So, reducing the latency treshold to declare high latency.
And also keeping track of lowest/highest per reporting window and
logging those along with short term and long term measurements.

NOTE: previously short term and long term were separate calls with locks
acquired. Now, it is all in one lock. So, it does increase the lock
duration a bit, but hopefully not by too much as the welford merge for
short term would go over 20 samples (at 50 ms sampling interval and 1 s
reporting window).

* revert skew factor