[CALCITE-6268] Support implementing custom JdbcSchema. Change comment #113

Job	Run time
CheckerFramework (JDK 11), oldest Guava	10m 16s
Error Prone (JDK 11), latest Guava	4m 46s
Linux (JDK 11), Avatica main	11m 28s
CheckerFramework (JDK 11)	9m 46s
Druid Tests	6m 53s
Linux (JDK 11), Pacific/Chatham Timezone	9m 23s
Linux (JDK 17)	9m 13s
Linux (JDK 19)	8m 48s
Linux (JDK 8), latest Guava, America/New_York Timezone	10m 42s
Linux (JDK 8), oldest Guava, America/New_York Timezone	9m 45s
Linux (JDK 8) Slow Tests	0s
macOS (JDK 19)	16m 8s
Windows (JDK 17)	13m 20s
Windows (JDK 8)	14m 55s
	2h 15m 23s

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