Restyle refactor: Use `merge_sort` instead of `qsort` for sorting. #5269

Job	Run time
docker-fuzzer	15s
docker-clusterfuzz	31s
docker-bootstrap-node	1m 31s
docker-toxcore-js	1m 51s
docker-esp32	1m 58s
docker-win32	15s
docker-win64	8s
docker-bootstrap-node-websocket	15s
	6m 44s

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