the current value of 256 limits the number of PDCP SDUs that can be
notified from RLC. The limit is quickly hit when too many SDUs
are in flight. This can cause unwanted log entries and weird PDCP
behaviour.
the patch increases the value to 1024, which still can be too few if
many smaller SDUs are traveling.
The patch also set the log level to warning to quicker spot
misconfigs in logs.
Fixes#2616
The window elements are not being correctly cleaned up when clear() is called
or when overwritten by newer SN. Furthermore, the window count member is not being
correctly updated when the insertion of a newer SN overwrites the previous one.
I used the circular_map container to avoid this sort of bugs