tests: subsys: logging: Add test for message drop notification
tests: subsys: logging: Add test for message drop notification

Extended logger suite to test correctness of reporting dropped
log messages.

Signed-off-by: Krzysztof Chruscinski <9b6dc988558c51b0405b49b55c8e66862969844b@nordicsemi.no>

GiulianoFranchetto/zephyr,punitvara/zephyr,finikorg/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,explora26/zephyr,explora26/zephyr,punitvara/zephyr,punitvara/zephyr,nashif/zephyr,Vudentz/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,ldts/zephyr,ldts/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,explora26/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,ldts/zephyr,Vudentz/zephyr,nashif/zephyr,Vudentz/zephyr,galak/zephyr,finikorg/zephyr,galak/zephyr,punitvara/zephyr,ldts/zephyr,nashif/zephyr,finikorg/zephyr,explora26/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,zephyrproject-rtos/zephyr,punitvara/zephyr,ldts/zephyr,GiulianoFranchetto/zephyr,galak/zephyr,galak/zephyr,nashif/zephyr,finikorg/zephyr,explora26/zephyr,GiulianoFranchetto/zephyr