Fix Deadlock from Thread.suspend in Test (elastic#39261)

* The lambda invoked by the `lockedExecutor` eventually gets JITed (which runs a static initializer that we will suspend in with a very tiny chance).
   * Fixed by creating the `Runnable` in the main test thread and using the same instance in all threads
* Closes elastic#35686

Author: original-brownbear

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

@@ -127,18 +127,18 @@ protected Pattern[] getUnsafeClasses() {
         final LockedExecutor lockedExecutor = new LockedExecutor();
         final AtomicLong ops = new AtomicLong();
         final Thread[] threads = new Thread[5];
+        final Runnable yieldAndIncrement = () -> {
+            Thread.yield(); // give some chance to catch this stack trace
+            ops.incrementAndGet();
+        };
         try {
             for (int i = 0; i < threads.length; i++) {
                 threads[i] = new Thread(() -> {
                     for (int iter = 0; stop.get() == false; iter++) {
                         if (iter % 2 == 0) {
-                            lockedExecutor.executeLocked(() -> {
-                                Thread.yield(); // give some chance to catch this stack trace
-                                ops.incrementAndGet();
-                            });
+                            lockedExecutor.executeLocked(yieldAndIncrement);
                         } else {
-                            Thread.yield(); // give some chance to catch this stack trace
-                            ops.incrementAndGet();
+                            yieldAndIncrement.run();
                         }
                     }
                 });