Migrate build to Gradle 9 #18

Job	Run time
Build scip-java CLI	4m 40s
gradle-java21-readiness	2m 8s
bazel-java-examples	2m 8s
gradle-kotlin-okio	2m 16s
gradle-kotlin-flowext	2m 6s
gradle-mixed-okio-jmh	2m 20s
maven-kotlin-json-kotlin-maven	2m 6s
maven-java17-spring-boot	2m 7s
	19m 51s

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