logging: Add handling of dropped messages to native POSIX backend
logging: Add handling of dropped messages to native POSIX backend

Extended native POSIX backend to handle dropped messages.

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

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