Add CancellationToken to `Async` members of `IChannel` #1295

Job	Run time
call-build-test / build-ubuntu	1m 2s
call-build-test / build-win32	2m 32s
call-build-test / integration-ubuntu	5m 42s
call-build-test / sequential-integration-ubuntu	2m 32s
call-build-test / integration-win32	13m 6s
call-build-test / sequential-integration-win32	6m 47s
	31m 41s

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