MINOR: quic-be: Parse the NEW_TOKEN frame

MINOR: quic-be: Parse the NEW_TOKEN frame

Rename ->data qf_new_token struct field to ->w_data to distinguish it from
->r_data new field used to parse the NEW_TOKEN frame. Indeed to build the
NEW_TOKEN we need to write it to a static buffer into the frame struct. To
parse it we only need to store the address of the token field into the
RX buffer.