[doc] add coro_rpc doc #1132

Job	Run time
ubuntu_clang (Release, OFF, ON)	1m 42s
ubuntu_clang_for_liburing (Release, OFF, ON)	1m 8s
ubuntu_clang_pb (Release, OFF, ON)	4m 20s
ubuntu_clang (Release, OFF, OFF)	2m 3s
ubuntu_clang_for_liburing (Debug, OFF, ON)	1m 56s
ubuntu_clang (Debug, OFF, ON)	2m 11s
ubuntu_clang_pb (Release, OFF, OFF)	4m 13s
ubuntu_clang (Debug, OFF, OFF)	1m 53s
ubuntu_clang_pb (Debug, OFF, ON)	3m 16s
ubuntu_clang10 (Release)	2m 41s
ubuntu_clang10 (Debug)	1m 58s
ubuntu_clang_pb (Debug, OFF, OFF)	3m 23s
	30m 44s

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