FP32 ReduceMean operator improvement #274

Job	Run time
select-env / select	3s
deeploy-typing	3m 9s
deeploy-state-serialization	3m 8s
deeploy-debug	3m 8s
deeploy-memory-level-extension	3m 10s
deeploy-memory-allocation	3m 10s
deeploy-memory-allocation-extension	3m 8s
deeploy-regex-matching	3m 9s
deeploy-tiler-extension	3m 9s
build-deeploy	3m 8s
deeploy-test-dmas	15m 26s
	43m 48s

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