[coro_io] add support for cancellation #1740

Job	Run time
ubuntu_clang_for_liburing (Release, OFF, ON)	4m 1s
ubuntu_clang (Release, OFF, ON)	3m 36s
ubuntu_clang_for_liburing (Debug, OFF, ON)	5m 8s
ubuntu_clang (Release, OFF, OFF)	3m 23s
ubuntu_clang_pb (Release, OFF, ON)	2m 10s
ubuntu_clang10 (Release)	44s
ubuntu_clang (Debug, OFF, ON)	5m 7s
ubuntu_clang_pb (Release, OFF, OFF)	2m 18s
ubuntu_clang10 (Debug)	39s
ubuntu_clang (Debug, OFF, OFF)	4m 59s
ubuntu_clang_pb (Debug, OFF, ON)	1m 55s
ubuntu_clang_pb (Debug, OFF, OFF)	1m 49s
	35m 49s

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