MINOR: quic: Stop storing the TX encoded transport parameters

MINOR: quic: Stop storing the TX encoded transport parameters

There is no need to keep an encoded version of the QUIC listener transport
parameters attache to the connection.

Remove ->enc_params and ->enc_params_len member of quic_conn struct.
Use variables to build the encoded transport parameter local to
ha_quic_set_encryption_secrets() before they are passed to
SSL_set_quic_transport_params().

Modify qc_ssl_sess_init() prototype. It was expected to be used with
the encoded transport parameters as passed parameter, but they were not
used. Cleanup this function.