[CALCITE-6720] Refactor cross product logic in RelMdUniqueKeys#getPas… #235

Job	Run time
CheckerFramework (JDK 11, oldest Guava)	11m 16s
ErrorProne (JDK 11, latest Guava)	7m 6s
CheckerFramework (JDK 11)	11m 3s
Linux (JDK 11, Avatica main)	16m 2s
Druid Tests	7m 45s
Linux (JDK 11, Pacific/Chatham Timezone)	11m 8s
Linux (JDK 17)	11m 5s
Linux (JDK 21)	11m 3s
Linux (JDK 23)	11m 4s
Linux (JDK 8, latest Guava, America/New_York Timezone)	13m 7s
Linux (JDK 8, oldest Guava, America/New_York Timezone)	11m 57s
Linux (JDK 8) Slow Tests	0s
macOS (JDK 21)	46m 52s
Windows (JDK 17)	17m 29s
Windows (JDK 21)	16m 20s
Windows (JDK 8)	16m 32s
	3h 39m 49s

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