If there is an event to be handled by _esp_eth_isr(), don't
overwrite it if a new packet has been received.
In my testing, all SYSTEM_EVENT_ETH_CONNECTED events except the first
are immediately followed by at least one SYSTEM_EVENT_ETH_RX_DONE event.
This causes the SYSTEM_EVENT_ETH_CONNECTED to not get handled, and the
IP stack will not be notified of the new link state.
Protect the other events by dropping the packet instead. If an earlier
unhandled SYSTEM_EVENT_ETH_RX_DONE event exists, overwrite it with the
newer packet.
I only saw this happen with lwIP and not with GNRC - I am not sure why.
But it still is a race waiting to happen. The nice long term solution
is probably to have a queue of unhandled events, allowing them all to
be processed once there is time.
The URI is passed as a string to `suit_coap_get_blockwise()`.
It may contain query parameters, those will not be translated
properly to CoAP options if `coap_opt_put_uri_path()` is used.
Instead use `coap_opt_put_uri()` to handle both path and query
parameters.
Lists state, link type, v4/v6 addresses.
Currently read-only.
Using lwIP debug system to print addresses, to limit dependencies
and work with dual stack setup. Most other code seems to only
allow either v4 or v6 networking. For that to compile I
had to change the `SZT_F` format string due to this error:
```
error: format '%lu' expects argument of type 'long unsigned int',
but argument 2 has type 'size_t {aka unsigned int}'
```
Switching to the lwIP default format string here.
Outputs the following on my ESP32 board with Ethernet,
when both v4 and v6 are enabled in examples/paho-mqtt:
```
> ifconfig
Iface ET0 HWaddr: 24:0a:c4:e6:0e:9f Link: up State: up
Link type: wired
inet addr: 10.4.4.81 mask: 255.255.254.0 gw: 10.4.4.1
inet6 addr: fe80:0:0:0:260a:c4ff:fee6:e9f scope: link
inet6 addr: 2001:db8:1000:0:260a:c4ff:fee6:e9f scope: global
Iface ET1 HWaddr: 24:0a:c4:e6:0e:9c Link: up State: up
Link type: wireless
inet addr: 10.4.4.82 mask: 255.255.254.0 gw: 10.4.4.1
inet6 addr: fe80:0:0:0:260a:c4ff:fee6:e9c scope: link
inet6 addr: 2001:db8:1000:0:260a:c4ff:fee6:e9c scope: global
>
```
