Cache result of _Reduce constructor #4481

Job	Run time
Build workflow from matrix	19s
Build and Verify Docs	7m 34s
Build MatX / Build MatX	3m 59s
Build RAPIDS / Check GH Event	2s
Build RAPIDS / rmm KvikIO cudf cudf_kafka cuspatial	5m 58s
Build RAPIDS / rmm ucxx raft cuvs	4m 20s
Build RAPIDS / rmm ucxx raft cumlprims_mg cuml	5m 4s
Build RAPIDS / rmm ucxx raft cugraph-ops wholegraph cugraph	7m 31s
${{ matrix.name }}	0s
${{ matrix.name }}	0s
${{ matrix.name }}	0s
Verify Dev Containers / Verify devcontainer files are up-to-date	27s
cuda (python) CTK12.6 nvcc GCC / [GCC13] Test(amd64, V100)	14m 53s
Verify Dev Containers / ${{ matrix.devcontainer.name }}	0s
Build MatX / Notify Slack of MatX failure	0s
Build RAPIDS / Notify Slack of RAPIDS failure	0s
Verify and summarize workflow results	17s
CI	1s
	50m 25s

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