MINOR: quic: implement delivery rate sampling algorithm

MINOR: quic: implement delivery rate sampling algorithm

This patch implements an algorithm which may be used by congestion algorithms
for QUIC to estimate the current delivery rate of a sender. It is at least used
by BBR and could be used by others congestion algorithms as cubic.

This algorithm was specified by an RFC draft here:
https://datatracker.ietf.org/doc/html/draft-cheng-iccrg-delivery-rate-estimation
before being merged into BBR v3 here:
https://datatracker.ietf.org/doc/html/draft-cardwell-ccwg-bbr#section-4.5.2.2