Add `AsyncEnumerable` #640

Job	Run time
Test (Release, Pool_Enabled)	48m 35s
Test (Release, Pool_Disabled)	39m 30s
Test (Release_NoProgress, Pool_Enabled)	38m 2s
Test (Release_NoProgress, Pool_Disabled)	33m 52s
Test (Debug, Pool_Disabled)	1h 0m 28s
Test (Debug_NoProgress, Pool_Disabled)	1h 3m 28s
	4h 43m 55s

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