MINOR: quic: use dynamic cc_algo on bind_conf

MINOR: quic: use dynamic cc_algo on bind_conf

A QUIC congestion algorithm can be specified on the bind line via
keyword quic-cc-algo. As such, bind_conf structure has a member
quic_cc_algo.

Previously, if quic-cc-algo was set, bind_conf member was initialized to
one of the globally defined CC algo structure. This patch changes
bind_conf quic_cc_algo initialization to point to a dynamically
allocated copy of CC algo structure.

With this change, it will be possible to tweak individually each CC algo
of a bind line. This will be used to activate pacing on top of the
congestion algorithm.

As bind_conf member is dynamically allocated now, its member is now
freed via free_proxy() to prevent any leak.