It is required to define a mandatory dependency on lwip, so we
introduced esp_netif_stack component and made it require lwip, instead
of directly depending on lwip.
This enables building w-out lwip and support other TCP/IP stacks.
This updates the minimal supported version of CMake to 3.16, which in turn enables us to use more CMake features and have a cleaner build system.
This is the version that provides most new features and also the one we use in our latest docker image for CI.
