Fix fully qualified names in stacktraces in tests

With move to JDK11, the `park` method changed its fully qualified
name.

Author: dkhalanskyjb

kotlinx-coroutines-debug/test/RunningThreadStackMergeTest.kt

@@ -20,7 +20,7 @@ class RunningThreadStackMergeTest : DebugTestBase() {
         verifyDump(
             "Coroutine \"coroutine#1\":BlockingCoroutine{Active}@62230679", // <- this one is ignored
             "Coroutine \"coroutine#2\":StandaloneCoroutine{Active}@50284dc4, state: RUNNING\n" +
-                    "\tat sun.misc.Unsafe.park(Native Method)\n" +
+                    "\tat jdk.internal.misc.Unsafe.park(Native Method)\n" +
                     "\tat java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)\n" +
                     "\tat java.util.concurrent.locks.AbstractQueuedSynchronizer\$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)\n" +
                     "\tat java.util.concurrent.CyclicBarrier.dowait(CyclicBarrier.java:234)\n" +
@@ -74,7 +74,7 @@ class RunningThreadStackMergeTest : DebugTestBase() {
         verifyDump(
             "Coroutine \"coroutine#1\":BlockingCoroutine{Active}@62230679", // <- this one is ignored
             "Coroutine \"coroutine#2\":StandaloneCoroutine{Active}@3aea3c67, state: RUNNING\n" +
-                    "\tat sun.misc.Unsafe.park(Native Method)\n" +
+                    "\tat jdk.internal.misc.Unsafe.park(Native Method)\n" +
                     "\tat java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)\n" +
                     "\tat java.util.concurrent.locks.AbstractQueuedSynchronizer\$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)\n" +
                     "\tat java.util.concurrent.CyclicBarrier.dowait(CyclicBarrier.java:234)\n" +
@@ -114,7 +114,7 @@ class RunningThreadStackMergeTest : DebugTestBase() {
         verifyDump(
             "Coroutine \"coroutine#1\":BlockingCoroutine{Active}@62230679", // <- this one is ignored
             "Coroutine \"coroutine#2\":StandaloneCoroutine{Active}@3aea3c67, state: RUNNING\n" +
-                    "\tat sun.misc.Unsafe.park(Native Method)\n" +
+                    "\tat jdk.internal.misc.Unsafe.park(Native Method)\n" +
                     "\tat java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)\n" +
                     "\tat java.util.concurrent.locks.AbstractQueuedSynchronizer\$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)\n" +
                     "\tat java.util.concurrent.CyclicBarrier.dowait(CyclicBarrier.java:234)\n" +