Add SINGLE_VALUE aggregate function #45423

Job	Run time
Java Wordcount Direct Runner (macos-latest)	13m 56s
Java Unit Tests (windows-latest)	13m 54s
Java Unit Tests (self-hosted, ubuntu-24.04, main)	20m 39s
Java Wordcount Direct Runner (windows-latest)	22m 38s
Java Wordcount Direct Runner (self-hosted, ubuntu-24.04, main)	19m 45s
Java Unit Tests (macos-latest)	14m 38s
	1h 45m 30s

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