Default to entitlements only for JDK 24+ (elastic#119885)

Since entitlements are still being developed, we are not yet ready to
enable them for all JDK versions. But we must use them for JDK 24+ since
the security manager is not useable there. This commit tweaks the logic
for determining whether to use entitlements to take into account  the
runtime version.

distribution/tools/server-cli/src/main/java/org/elasticsearch/server/cli/SystemJvmOptions.java

@@ -11,6 +11,7 @@
 
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.util.concurrent.EsExecutors;
+import org.elasticsearch.core.Booleans;
 import org.elasticsearch.core.UpdateForV9;
 import org.elasticsearch.jdk.RuntimeVersionFeature;
 
@@ -26,7 +27,9 @@ final class SystemJvmOptions {
     static List<String> systemJvmOptions(Settings nodeSettings, final Map<String, String> sysprops) {
         String distroType = sysprops.get("es.distribution.type");
         boolean isHotspot = sysprops.getOrDefault("sun.management.compiler", "").contains("HotSpot");
-        boolean useEntitlements = Boolean.parseBoolean(sysprops.getOrDefault("es.entitlements.enabled", "false"));
+        boolean entitlementsExplicitlyEnabled = Booleans.parseBoolean(sysprops.getOrDefault("es.entitlements.enabled", "false"));
+        // java 24+ only supports entitlements, but it may be enabled on earlier versions explicitly
+        boolean useEntitlements = RuntimeVersionFeature.isSecurityManagerAvailable() == false || entitlementsExplicitlyEnabled;
         return Stream.of(
             Stream.of(
                 /*

server/src/main/java/org/elasticsearch/bootstrap/Elasticsearch.java

@@ -28,6 +28,7 @@
 import org.elasticsearch.common.transport.BoundTransportAddress;
 import org.elasticsearch.common.util.concurrent.RunOnce;
 import org.elasticsearch.core.AbstractRefCounted;
+import org.elasticsearch.core.Booleans;
 import org.elasticsearch.core.IOUtils;
 import org.elasticsearch.core.SuppressForbidden;
 import org.elasticsearch.entitlement.bootstrap.EntitlementBootstrap;
@@ -109,7 +110,9 @@ private static Bootstrap initPhase1() {
         final PrintStream out = getStdout();
         final PrintStream err = getStderr();
         final ServerArgs args;
-        final boolean useEntitlements = Boolean.parseBoolean(System.getProperty("es.entitlements.enabled"));
+        final boolean entitlementsExplicitlyEnabled = Booleans.parseBoolean(System.getProperty("es.entitlements.enabled", "false"));
+        // java 24+ only supports entitlements, but it may be enabled on earlier versions explicitly
+        final boolean useEntitlements = RuntimeVersionFeature.isSecurityManagerAvailable() == false || entitlementsExplicitlyEnabled;
         try {
             initSecurityProperties();