Refactor WindowOperatorQueryKit to use WindowStage class for representing different window stages #13237

Job	Run time
Set env var	1s
build (jdk8)	11m 23s
build (jdk11)	11m 22s
build (jdk17)	11m 22s
build (jdk21.0.4)	11m 23s
unit tests (jdk8, sql-compat=${{ matrix.sql_compatibility }})	1s
unit tests (jdk${{ matrix.jdk }}, sql-compat=true)	1s
standard-its	1s
revised-its	1s
	45m 35s

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