[CALCITE-6749] RelMdUtil#setAggChildKeys may return an incorrect result #14413

Job	Run time
Windows (JDK 17)	16m 11s
Windows (JDK 8)	16m 15s
Linux (JDK 8, oldest Guava, America/New_York Timezone)	10m 57s
Windows (JDK 21)	15m 6s
Linux (JDK 11, Pacific/Chatham Timezone)	10m 26s
Linux (JDK 8, latest Guava, America/New_York Timezone)	12m 8s
Linux (JDK 21)	12m 22s
Linux (JDK 17)	12m 24s
ErrorProne (JDK 11, latest Guava)	6m 24s
Linux (JDK 11, Avatica main)	17m 1s
CheckerFramework (JDK 11)	13m 37s
CheckerFramework (JDK 11, oldest Guava)	13m 21s
Linux (JDK 23)	10m 22s
macOS (JDK 21)	41m 27s
Druid Tests	9m 16s
Linux (JDK 8) Slow Tests	0s
	3h 37m 17s

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