MINOR: quic: Dynamic packet reordering threshold

MINOR: quic: Dynamic packet reordering threshold

Let's say that the largest packet number acknowledged by the peer is #10, when inspecting
the non already acknowledged packets to detect if they are lost or not, this is the
case a least if the difference between this largest packet number and and their
packet numbers are bigger or equal to the packet reordering threshold as defined
by the RFC 9002. This latter must not be less than QUIC_LOSS_PACKET_THRESHOLD(3).
Which such a value, packets #7 and oldest are detected as lost if non acknowledged,
contrary to packet number #8 or #9.

So, the packet loss detection is very sensitive to such a network characteristic
where non acknowledged packets are distant from each others by their packet number
differences.

Do not use this static value anymore for the packet reordering threshold which is used
as a criteria to detect packet loss. In place, make it depend on the difference
between the number of the last transmitted packet and the number of the oldest
one among the packet which are still in flight before being inspected to be
deemed as lost.

Add new tune.quic.reorder-ratio setting to apply a ratio in percent to this
dynamic packet reorder threshold.

Should be backported to 2.6.