MINOR: quic: define max-window-size config setting

MINOR: quic: define max-window-size config setting

Define a new global keyword tune.quic.frontend.max-window-size. This
allows to set globally the maximum congestion window size for each QUIC
frontend connections.

The default value is 0. It is a special value which automatically derive
the size from the configured QUIC connection buffer limit. This is
similar to the previous "quic-cc-algo" behavior, which can be used to
override the maximum window size per bind line.