MINOR: quic-be: helper functions to save/restore transport params (0-RTT)

MINOR: quic-be: helper functions to save/restore transport params (0-RTT)

Define quic_early_transport_params new struct for QUIC transport parameters
in relation with 0-RTT. This parameters must be saved during a first session to
be reused for 0-RTT next sessions.

qc_early_transport_params_cpy() copies the 0-RTT transport parameters to be
saved during a first connection to a backend. The copy is made from
a quic_transport_params struct to a quic_ealy_transport_params struct.

On the contrary, qc_early_transport_params_reuse() copies the transport parameters
to be reused for a 0-RTT session from a previous one. The copy is made
from a quic_early_transport_params strcut to a quic_transport_params struct.

Also add QUIC_EV_EARLY_TRANSP_PARAMS trace event to dump such 0-RTT
transport parameters from traces.