lwip/netif struct has two places to store user's data
* netif->state (1 void*) but that might be occupied in special cases
* netif->client_dtat (n void*s) but that must be enabled in opts.h
This commit stores esp_netif_t* primarily in state, but if any special
netif is enabled in menuconfig (bridgeif, pppos), it uses netif->client_data.
This commit also fixes incorrect esp_netif that is attached to
IP_EVENT_GOT_IP6 event posted by pppos interfaces in:
c585618b97/components/esp_netif/lwip/esp_netif_lwip_ppp.c (L114)
Closes https://github.com/espressif/esp-idf/issues/9345
Fix dependency tree so that lwip doesn't depend on any specific network
interface component.
Network interface drivers shall depend on esp_netif.
esp_netif shall depend on lwip (but not on any specific interface
driver) -- it optionally depends on vfs and esp_eth (need ethernet
header for L2/bridge mode)
