tests: net: coap: Acknowledgement initialization
tests: net: coap: Acknowledgement initialization

New test that verifies CoAP Acknowledgement initialization function
that create a response packet for given request. Both request and
expected response packets are given in the test as PDU.

Signed-off-by: Hubert Miś <a91fd59c670965fa0579dbce0eafdaab862c821f@nordicsemi.no>

Vudentz/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,galak/zephyr,galak/zephyr,galak/zephyr,nashif/zephyr,nashif/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,Vudentz/zephyr,finikorg/zephyr,Vudentz/zephyr,nashif/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,finikorg/zephyr,galak/zephyr,Vudentz/zephyr,finikorg/zephyr