refactor: migrate Xtend to Java - com.avaloq.tools.ddk.sample.helloworld.ui.test

[joaodinissf]

Migrates the last three Xtend files in the sample.helloworld.* bundles to Java 21, taking the bundle family fully off Xtend.

Migration (com.avaloq.tools.ddk.sample.helloworld.ui.test)

• CheckConfigurationIsAppliedTest, CheckExecutionEnvironmentProjectTest, IssueLabelTest converted to Java; .xtend originals deleted.
• Module infrastructure cleaned up: xtend-gen removed from .classpath and build.properties, xtend-gen/.gitignore deleted, Xtext builder/nature removed from .project.

Intentional deviations from the Xtend compiler output, all behavior-equivalent:

• Test methods declare throws Exception instead of Xtend's generated sneakyThrow wrapping.
• getInjector() is protected, matching the AbstractCheckTestCase supertype (Xtend widened it to public); all call sites are internal to the test framework.
• List.of/Map.of replace Lists.newArrayList/newHashMap for the collection literals — consumers only iterate them.

Stale Xtend dependency cleanup (sibling bundles)

org.eclipse.xtend.lib is removed from the helloworld, helloworld.ide, and helloworld.ui manifests. The only remaining source reference was the inert @FinalFieldsConstructor annotation on HelloWorldUiModule — an Xtend active annotation that generates nothing in Java source (the constructor it would generate is declared explicitly right below it) — which is dropped along with its import. No source in these bundles references org.eclipse.xtend.* or org.eclipse.xtend2.* after this change.

Verification

Full mvn verify with Checkstyle and PMD: BUILD SUCCESS, 357/357 tests passing, including all 7 test methods of the migrated classes (via HelloWorldSampleTestSuite in AllTests).

🤖 Generated with Claude Code