Update groupItems to use less memory #3835

Job	Run time
paths-filter	8s
Integration Tests	3m 44s
Build Binary	2m 46s
E2E	5m 21s
Analyzers Unit Tests	45s
Datastore Consistency Tests (crdb)	2m 45s
Build Container Image	4m 26s
Unit	3m 1s
Datastore Consistency Tests (mysql)	2m 41s
Datastore Tests (crdb)	3m 13s
Datastore Consistency Tests (postgres)	2m 31s
Datastore Tests (mysql)	3m 49s
WASM Tests	1m 38s
Datastore Consistency Tests (spanner)	2m 8s
Generate Protobufs	0s
Datastore Tests (postgres)	4m 50s
Datastore Tests (spanner)	1m 52s
	45m 38s

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