BUILD: quic: fix overflow in global tune

BUILD: quic: fix overflow in global tune

A new global option was recently introduced to disable pacing. However,
the value used (1<<31) caused issue with some compiler as options field
used for storage is declared as int. Move pacing deactivation flag
outside into the newly defined quic_tune to fix this.

This should be backported up to 3.1 after a period of observation. Note
that it relied on the previous patch which defined new quic_tune type.

(cherry picked from commit b849ee5fa35b7a909869db1dfd19f450f3172034)
[ada: patch was manually adapted since a19d9b0486 ("MAJOR: quic: mark
 pacing as stable and enable it by default") was not backported]
Signed-off-by: Aurelien DARRAGON <adarragon@haproxy.com>