Fix Gradle nativeTest test resource detection

[jormundur00]

Fixes #537

Spec Fit

Issue 537 reports that Gradle nativeTest omits resources from src/test/resources, even though ordinary JVM test sees them. Existing native-test specs already require the Gradle test binary to derive classes, resources, classpath, test identifiers, and JUnit support from the Gradle test source set/task, so no spec change was needed.

Relevant behavior is covered by gradle/FS-gradle-native-tests.1, gradle/FS-gradle-native-image-tasks.1, and root/FS-native-tests.2.

Implementation Summary

• Enables resource autodetection by convention for the Gradle native test binary.
• Excludes generated junit-platform-unique-ids.* discovery-list files from detected test resources.
• Adds a focused functional regression that creates src/test/resources/db/mysql_conf_override, runs nativeTest without explicit resource configuration, and verifies the native test executable can load the resource.
• Adds a changelog entry for the nativeTest resource fix.

Validation Evidence

Passed locally:

• JAVA_HOME=/home/jovan/.sdkman/candidates/java/17.0.12-graal GRAALVM_HOME=/home/jovan/.sdkman/candidates/java/21.0.11-graal ./gradlew :native-gradle-plugin:functionalTest --tests "org.graalvm.buildtools.gradle.JavaApplicationWithResourcesFunctionalTest.native tests include test resources without explicit resource configuration"
• JAVA_HOME=/home/jovan/.sdkman/candidates/java/17.0.12-graal GRAALVM_HOME=/home/jovan/.sdkman/candidates/java/17.0.12-graal ./gradlew :native-gradle-plugin:inspections
• git diff --check

Not completed locally:

• grund check is currently blocked before patch-specific citation validation by repository-wide stale grund init blocks in AGENTS files.
• Full repository CI, ./gradlew build, and the full :native-gradle-plugin:functionalTest suite were not run locally.
• The external Testcontainers/MySQL reproducer from the issue was not run; the in-repository regression covers the missing classpath-resource behavior directly.

Review Readiness

Draft PR. Agent review found no requirements, spec/grounding, implementation, or validation blockers. Remaining validation gaps are documented above.

Remaining Human Follow-up

• Review the behavioral default change for Gradle native-test resource autodetection.
• Run full CI or full Gradle functional coverage if desired before marking ready for review.