drm_hwcomposer: Add test utility to listen for uevents

Dumping uevents is useful for debugging purposes.

1. Extract logic related to uevent socket into utils/UEvent.h class.
2. Use it by both UEventListener.cpp and tests/uevent_print.cpp.

Bump clang-tidy level of UEventListener.cpp to normal.

Signed-off-by: Roman Stratiienko <roman.o.stratiienko@globallogic.com>
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