* remove unused bool return value from sentPacketHandler.getPTOTimeAndSpace
* ackhandler: implement timer logic for path probing packets
Path probe packets are treated differently from regular packets: The new
path might have a vastly different RTT than the original path.
Path probe packets are declared lost 1s after they are sent. This value
can be reduced, once implement proper retransmission logic for lost path
probes.
* ackhandler: declare path probes lost on OnLossDetectionTimeout
* ackhandler: detect ECN mangling
Mangling means that a path is re-marking all ECN-marked packets as CE.
* ackhandler: only detect ECN mangling once all testing packets were sent
The enums have completely different meanings. protocol.PacketType only
defines long header types, whereas logging.PacketType defines all
different types of QUIC packets (including short header packets).
