MINOR: quic: Stop stressing the acknowledgments process (RX ACK frames)

MINOR: quic: Stop stressing the acknowledgments process (RX ACK frames)

The ACK frame range of packets were handled from the largest to the smallest
packet number, leading to big number of ebtree insertions when the packet are
handled in the inverse way they are sent. This was detected a long time ago
but left in the code to stress our implementation. It is time to be more
efficient and process the packet so that to avoid useless ebtree insertions.

Modify qc_ackrng_pkts() responsible of handling the acknowledged packets from an
ACK frame range of acknowledged packets.

Must be backported to 2.7.