Add Docker based testing support to network samples

[jukkar]

We have infrastructure to run network samples against a Docker container running Linux, see information at https://github.com/zephyrproject-rtos/zephyr/blob/master/scripts/net/README.txt.

Collect here a list of network samples that work properly with the runner script so we can track the progress.

Status	Sample	Comment
	dhcpv4_client
	dns_resolve	#30778 and zephyrproject-rtos/net-tools#55
✔️	gptp	#29646
	ipv4_autoconf
	lldp
✔️	lwm2m_client
✔️	LwM2M interoperability tests with Leshan
	mdns_responder
✔️	mqtt_publisher	Already supported, both plain and TLS communication tested and were working, the proxy tests are disabled and need more work
	promiscuous_mode
✔️	syslog_net	#30439
	telnet
	vlan
	big_http_download
	can	The CAN testing could be based on this zephyrproject-rtos/net-tools#26
	civetweb	Multiple civetweb applications exists, this needs to be opened up in the future. Civetweb removed from upstream zephyr so this is no longer applicable
	coap_client
✔️	coap_server	Already supported, tested with etsi_testcases.sh script found in libcoap in net-tools
	dumb_http_server
✔️	dumb_http_server_mt	#29948
✔️	echo_client	Already supported
✔️	echo_server	Already supported
✔️	http_client	#29892
	http_get
	packet
	sntp_client
	websocket_client

Original issue at #19540

[jukkar]

Short presentation about Docker based testing https://drive.google.com/file/d/1LYPcVOyHrJGUaD4wuAwZYlBq310jgVV_/view

[KozhinovAlexander]

Please note #30175 for CivetWeb