Migrate build to Gradle 9 #17

Job	Run time
Build scip-java CLI	3m 57s
gradle-mixed-okio-jmh	3m 24s
gradle-java21-readiness	1m 43s
bazel-java-examples	2m 50s
maven-java17-spring-boot	1m 38s
gradle-kotlin-okio	4m 32s
gradle-kotlin-flowext	4m 3s
maven-kotlin-json-kotlin-maven	2m 52s
	24m 59s

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