CLEANUP: quic: remove unused qc param on stateless reset token

CLEANUP: quic: remove unused qc param on stateless reset token

Remove quic_conn instance as first parameter of
quic_stateless_reset_token_init() and quic_stateless_reset_token_cpy()
functions. It was only used for trace purpose.

The main advantage is that it will be possible to allocate a QUIC CID
without a quic_conn instance using new_quic_cid() which is requires to
first check if a CID is existing before allocating a connection.

This should be backported up to 2.7.