BUG/MINOR: quic: Speed up the handshake completion only one time

It is possible to speed up the handshake completion but only one time
by connection as mentionned in RFC 9002 "6.2.3. Speeding up Handshake Completion".
Add a flag to prevent this process to be run several times
(see https://www.rfc-editor.org/rfc/rfc9002#name-speeding-up-handshake-compl).

Must be backported to 2.6.
2 files changed