Remove pesky restricted method warnings in tests.

Since our unit and IT tests run as unnamed modules we should add `--enable-native-access=ALL-UNNAMED` to suppress the pesky warning that arise from calls to `System::load`.

Author: ChrisHegarty

build-tools-internal/src/main/java/org/elasticsearch/gradle/internal/ElasticsearchTestBasePlugin.java

@@ -120,6 +120,7 @@ public void execute(Task t) {
                 "--add-opens=java.base/java.nio.file=ALL-UNNAMED",
                 "--add-opens=java.base/java.time=ALL-UNNAMED",
                 "--add-opens=java.management/java.lang.management=ALL-UNNAMED",
+                "--enable-native-access=ALL-UNNAMED",
                 "-XX:+HeapDumpOnOutOfMemoryError"
             );