Refactor Wifi indoor positioning example to accept a custom network identifier instead of SSID

[eloquentarduino]

To accomodate Wifi repeaters, allow the user to specify a custom function to identify an AP, for example joining SSID + MAC address.

Take a look at

esp_wifi_set_promiscuous(true);
esp_wifi_set_promiscuous_rx_cb(&wifi_sniffer_packet_handler);

void wifi_sniffer_packet_handler(void* buff, wifi_promiscuous_pkt_type_t type)
{
  if (type != WIFI_PKT_MGMT)
    return;

  const wifi_promiscuous_pkt_t *ppkt = (wifi_promiscuous_pkt_t *)buff;
  const wifi_ieee80211_packet_t *ipkt = (wifi_ieee80211_packet_t *)ppkt->payload;
  const wifi_ieee80211_mac_hdr_t *hdr = &ipkt->hdr;

  printf("PACKET TYPE=%s, CHAN=%02d, RSSI=%02d,"
    " ADDR1=%02x:%02x:%02x:%02x:%02x:%02x,"
    " ADDR2=%02x:%02x:%02x:%02x:%02x:%02x,"
    " ADDR3=%02x:%02x:%02x:%02x:%02x:%02x\n",
    wifi_sniffer_packet_type2str(type),
    ppkt->rx_ctrl.channel,
    ppkt->rx_ctrl.rssi,
    /* ADDR1 */
    hdr->addr1[0],hdr->addr1[1],hdr->addr1[2],
    hdr->addr1[3],hdr->addr1[4],hdr->addr1[5],
    /* ADDR2 */
    hdr->addr2[0],hdr->addr2[1],hdr->addr2[2],
    hdr->addr2[3],hdr->addr2[4],hdr->addr2[5],
    /* ADDR3 */
    hdr->addr3[0],hdr->addr3[1],hdr->addr3[2],
    hdr->addr3[3],hdr->addr3[4],hdr->addr3[5]
  );
}