Migrate build to Gradle 9 #19

Job	Run time
Build scip-java CLI	5m 5s
gradle-kotlin-okio	4m 33s
gradle-kotlin-flowext	3m 59s
gradle-java21-readiness	1m 39s
maven-kotlin-json-kotlin-maven	3m 12s
maven-java17-spring-boot	2m 58s
bazel-java-examples	1m 36s
gradle-mixed-okio-jmh	4m 25s
	27m 27s

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