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:

netbeans/.github/workflows/main.yml

Lines 2501 to 2503 in a1a87f5

	# TODO uses GraalVM 17 / 22.3.1 which is the last known release which offers all required language extensions
	# GraalVM based on JDK 21+ doesn't support the 'gu' tool anymore - extensions are now regular application dependencies
	graal: [ '22.3.1' ]

due to #6925, details: #6925 (comment)