Basically: * "classification by-ip" (i.e. `flow->guessed_protocol_id_by_ip` is NEVER returned in the protocol stack (i.e. `flow->detected_protocol_stack[]`); * if the application is interested into such information, it can access `ndpi_protocol->protocol_by_ip` itself. There are mainly 4 points in the code that set the "classification by-ip" in the protocol stack: the generic `ndpi_set_detected_protocol()`/ `ndpi_detection_giveup()` functions and the HTTP/STUN dissectors. In the unit tests output, a print about `ndpi_protocol->protocol_by_ip` has been added for each flow: the huge diff of this commit is mainly due to that. Strictly speaking, this change is NOT an API/ABI breakage, but there are important differences in the classification results. For examples: * TLS flows without the initial handshake (or without a matching SNI/certificate) are simply classified as `TLS`; * similar for HTTP or QUIC flows; * DNS flows without a matching request domain are simply classified as `DNS`; we don't have `DNS/Google` anymore just because the server is 8.8.8.8 (that was an outrageous behaviour...); * flows previusoly classified only "by-ip" are now classified as `NDPI_PROTOCOL_UNKNOWN`. See #1425 for other examples of why adding the "classification by-ip" in the protocol stack is a bad idea. Please, note that IPV6 is not supported :( (long standing issue in nDPI) i.e. `ndpi_protocol->protocol_by_ip` wil be always `NDPI_PROTOCOL_UNKNOWN` for IPv6 flows. Define `NDPI_CONFIDENCE_MATCH_BY_IP` has been removed. Close #1687