Add support for custom Ethernet timeouts

[manchoz]

This PR adds support for specifying custom timeouts on Ethernet connections.

Combined with the ArduinoIoTCloud library, this PR allows writing sketches that don't block for 15s in the loop() if the Ethernet cable is not connected or there is no link-layer connectivity.

To be used as:

EthernetConnectionHandler ArduinoIoTPreferredConnection(IP, DNS, GATEWAY, NETMASK, 1000);

  auto connStatus = ArduinoIoTPreferredConnection.check();

  if (connStatus == NetworkConnectionState::CONNECTED)
    ArduinoCloud.update();

[github-actions]

Memory usage change @ 36aa008

Board	flash	%	RAM for global variables	%
arduino:esp32:nano_nora	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:mbed:envie_m7	N/A	N/A	N/A	N/A
arduino:mbed_edge:edge_control	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:mbed_giga:giga	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:mbed_nano:nanorp2040connect	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:mbed_nicla:nicla_vision	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:mbed_opta:opta	🔺 +160 - +160	+0.01 - +0.01	🔺 +32 - +32	+0.01 - +0.01
arduino:mbed_portenta:envie_m7	N/A	N/A	N/A	N/A
arduino:renesas_portenta:portenta_c33	🔺 +136 - +136	+0.01 - +0.01	🔺 +32 - +32	+0.01 - +0.01
arduino:renesas_uno:unor4wifi	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:samd:mkr1000	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:samd:mkrgsm1400	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:samd:mkrnb1500	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:samd:mkrwan1300	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:samd:mkrwan1310	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:samd:mkrwifi1010	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:samd:nano_33_iot	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0
esp32:esp32:esp32	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0
esp8266:esp8266:huzzah	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0

Click for full report table

Board	examples/ConnectionHandlerDemo flash	%	examples/ConnectionHandlerDemo RAM for global variables	%
arduino:esp32:nano_nora	0	0.0	0	0.0
arduino:mbed:envie_m7	N/A	N/A	N/A	N/A
arduino:mbed_edge:edge_control	0	0.0	0	0.0
arduino:mbed_giga:giga	0	0.0	0	0.0
arduino:mbed_nano:nanorp2040connect	0	0.0	0	0.0
arduino:mbed_nicla:nicla_vision	0	0.0	0	0.0
arduino:mbed_opta:opta	160	0.01	32	0.01
arduino:mbed_portenta:envie_m7	N/A	N/A	N/A	N/A
arduino:renesas_portenta:portenta_c33	136	0.01	32	0.01
arduino:renesas_uno:unor4wifi	0	0.0	0	0.0
arduino:samd:mkr1000	0	0.0	0	0.0
arduino:samd:mkrgsm1400	0	0.0	0	0.0
arduino:samd:mkrnb1500	0	0.0	0	0.0
arduino:samd:mkrwan1300	0	0.0	0	0.0
arduino:samd:mkrwan1310	0	0.0	0	0.0
arduino:samd:mkrwifi1010	0	0.0	0	0.0
arduino:samd:nano_33_iot	0	0.0	0	0.0
esp32:esp32:esp32	0	0.0	0	0.0
esp8266:esp8266:huzzah	0	0.0	0	0.0

Click for full report CSV

Board,examples/ConnectionHandlerDemo<br>flash,%,examples/ConnectionHandlerDemo<br>RAM for global variables,%
arduino:esp32:nano_nora,0,0.0,0,0.0
arduino:mbed:envie_m7,N/A,N/A,N/A,N/A
arduino:mbed_edge:edge_control,0,0.0,0,0.0
arduino:mbed_giga:giga,0,0.0,0,0.0
arduino:mbed_nano:nanorp2040connect,0,0.0,0,0.0
arduino:mbed_nicla:nicla_vision,0,0.0,0,0.0
arduino:mbed_opta:opta,160,0.01,32,0.01
arduino:mbed_portenta:envie_m7,N/A,N/A,N/A,N/A
arduino:renesas_portenta:portenta_c33,136,0.01,32,0.01
arduino:renesas_uno:unor4wifi,0,0.0,0,0.0
arduino:samd:mkr1000,0,0.0,0,0.0
arduino:samd:mkrgsm1400,0,0.0,0,0.0
arduino:samd:mkrnb1500,0,0.0,0,0.0
arduino:samd:mkrwan1300,0,0.0,0,0.0
arduino:samd:mkrwan1310,0,0.0,0,0.0
arduino:samd:mkrwifi1010,0,0.0,0,0.0
arduino:samd:nano_33_iot,0,0.0,0,0.0
esp32:esp32:esp32,0,0.0,0,0.0
esp8266:esp8266:huzzah,0,0.0,0,0.0