Some tests fail on JDK 21+

[mbien]

see TODOs in https://github.com/apache/netbeans/blob/master/.github/workflows/main.yml

current list of JDK 17 locked tests is:

java/java.mx.project
java/gradle.java
extide/gradle
java/gradle.dependencies
extide/o.apache.tools.ant.module
apisupport/apisupport.ant

and the full GraalVM job: https://github.com/apache/netbeans/blob/a1a87f5bdc2c8e7467616250665e02e11af92674/.github/workflows/main.yml#L2501-L2503 due to https://github.com/apache/netbeans/issues/6925, details: https://github.com/apache/netbeans/issues/6925#issuecomment-2003319844