BUG/MAJOR: quic: reject invalid token

BUG/MAJOR: quic: reject invalid token

Token parsing code on INITIAL packet for the NEW_TOKEN format is not
robust enough and may even crash on some rare malformed packets.

This patch fixes this by adding a check on the expected length of the
received token. The packet is now rejected if the token does not match
QUIC_TOKEN_LEN. This check is legitimate as haproxy should only parse
tokens emitted by itself.

This issue has been introduced with the implementation of NEW_TOKEN
tokens parsing required for 0-RTT support.

This issue is assigned to CVE-2026-26081 report.

This must be backported up to 3.0.

Reported-by: Asim Viladi Oglu Manizada <manizada@pm.me>