Migrate build to Gradle 9 #23

Job	Run time
Build scip-java CLI	4m 15s
gradle-java21-readiness	2m 47s
gradle-kotlin-flowext	3m 36s
gradle-kotlin-okio	4m 35s
maven-java17-spring-boot	1m 41s
bazel-java-examples	1m 32s
gradle-mixed-okio-jmh	4m 47s
maven-kotlin-json-kotlin-maven	2m 48s
	26m 1s

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