Fix command graph generation bugs around reductions #3043

Job	Run time
find-duplicate-workflows	7s
clang-tidy	5m 9s
read-build-matrix	8s
build-and-test (dpcpp, 61e51015, 20.04, intel, Debug)	4m 37s
build-and-test (dpcpp, latest, 22.04, intel, Debug)	5m 42s
build-and-test (dpcpp, latest, 22.04, intel, Release)	4m 17s
build-and-test (hipsycl, d2bd9fc7, 20.04, nvidia, Debug)	9m 19s
build-and-test (hipsycl, d2bd9fc7, 22.04, nvidia, Debug)	11m 45s
build-and-test (hipsycl, d2bd9fc7, 22.04, nvidia, Release)	17m 50s
build-and-test (hipsycl, latest, 23.04, nvidia, Debug)	11m 44s
build-and-test (hipsycl, latest, 23.04, nvidia, Release)	18m 15s
report	17s
tag-latest-containers	0s
	1h 29m 10s

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