Mute disruption tests for jdk20+ (#94207)

In JDK 20 Thread suspend/resume is soft removed (they now throw
UnsupportedOperationException). Many ES disruption tests simulate GC
pauses with suspend/resume. As that strategy will no longer work, this
commit mutes those tests for jdk20+.

relates #94206
closes #93707

server/src/internalClusterTest/java/org/elasticsearch/discovery/StableMasterDisruptionIT.java

@@ -226,6 +226,7 @@ private void testFollowerCheckerAfterMasterReelection(NetworkLinkDisruptionType
      * following another elected master node. These nodes should reject this cluster state and prevent them from following the stale master.
      */
     public void testStaleMasterNotHijackingMajority() throws Exception {
+        assumeFalse("jdk20 removed thread suspend/resume", Runtime.version().feature() >= 20);
         final List<String> nodes = internalCluster().startNodes(
             3,
             Settings.builder()
@@ -333,6 +334,7 @@ public void onFailure(Exception e) {
      * @throws Exception
      */
     public void testRepeatedMasterChanges(String expectedMasterStabilitySymptomSubstring) throws Exception {
+        assumeFalse("jdk20 removed thread suspend/resume", Runtime.version().feature() >= 20);
         final List<String> nodes = internalCluster().startNodes(
             3,
             Settings.builder()
@@ -422,6 +424,7 @@ public void testRepeatedMasterChanges(String expectedMasterStabilitySymptomSubst
     }
 
     public void testRepeatedNullMasterRecognizedAsGreenIfMasterDoesNotKnowItIsUnstable() throws Exception {
+        assumeFalse("jdk20 removed thread suspend/resume", Runtime.version().feature() >= 20);
         /*
          * In this test we have a single master-eligible node. We pause it repeatedly (simulating a long GC pause for example) so that
          * other nodes decide it is no longer the master. However since there is no other master-eligible node, another node is never

test/framework/src/test/java/org/elasticsearch/test/disruption/LongGCDisruptionTests.java

@@ -9,6 +9,7 @@
 
 import org.elasticsearch.core.Nullable;
 import org.elasticsearch.test.ESTestCase;
+import org.junit.BeforeClass;
 
 import java.lang.management.ThreadInfo;
 import java.util.ArrayList;
@@ -40,6 +41,11 @@ public void executeLocked(Runnable r) {
         }
     }
 
+    @BeforeClass
+    public static void ignoreJdk20Plus() {
+        assumeFalse("jdk20 removed thread suspend/resume", Runtime.version().feature() >= 20);
+    }
+
     public void testBlockingTimeout() throws Exception {
         final String nodeName = "test_node";
         LongGCDisruption disruption = new LongGCDisruption(random(), nodeName) {