MINOR: qc_new_conn() rework for stateless reset

MINOR: qc_new_conn() rework for stateless reset

The stateless reset token of a connection is generated from qc_new_conn() when
allocating the first connection ID. A QUIC server can copy it into its transport
parameters to allow the peer to reset the associated connection.
This latter is not easily reachable after having returned from qc_new_conn().
We want to be able to initialize the transport parameters from this function which
has an access to all the information to do so.

Extract the code used to initialize the transport parameters from qc_lstnr_pkt_rcv()
and make it callable from qc_new_conn(). qc_lstnr_params_init() is implemented
to accomplish this task for a haproxy listener.
Modify qc_new_conn() to reduce its the number of parameters.
The source address coming from Initial packets is also copied from qc_new_conn().