Update JVMTI monitor functions

Support for virtual threads added in the following JVMTI functions:
- GetOwnedMonitorInfo
- GetOwnedMonitorStackDepthInfo
- GetCurrentContendedMonitor

Related changes: eclipse-openj9#15857

GetThreadState and GetThreadInfo allow a NULL input thread. In such
a case, they should look at the current thread's object. Because using
the NULL input thread causes a seg fault. This has been fixed.

Related issue: eclipse-openj9#15759

Co-authored-by: Gengchen Tuo <gengchen.tuo@ibm.com>
Co-authored-by: Jack Lu <Jack.S.Lu@ibm.com>
Signed-off-by: Babneet Singh <sbabneet@ca.ibm.com>

runtime/jvmti/jvmtiHelpers.c

@@ -1929,3 +1929,24 @@ genericWalkStackFramesHelper(J9VMThread *currentThread, J9VMThread *targetThread
 
  return rc;
 }
+
+#if JAVA_SPEC_VERSION >= 19
+J9VMContinuation *
+getJ9VMContinuationToWalk(J9VMThread *currentThread, J9VMThread *targetThread, j9object_t threadObject)
+{
+ J9VMContinuation *continuation = NULL;
+ if (IS_VIRTUAL_THREAD(currentThread, threadObject)) {
+ if (NULL == targetThread) {
+ /* An unmounted virtual thread will have a valid J9VMContinuation. */
+ j9object_t contObject = (j9object_t)J9VMJAVALANGVIRTUALTHREAD_CONT(currentThread, threadObject);
+ continuation = J9VMJDKINTERNALVMCONTINUATION_VMREF(currentThread, contObject);
+ }
+ } else {
+ /* J9VMThread->currentContinuation is set to NULL if a virtual thread is not mounted.
+ * If a virtual thread is mounted, currentContinuation stores the carrier thread details.
+ */
+ continuation = targetThread->currentContinuation;
+ }
+ return continuation;
+}
+#endif /* JAVA_SPEC_VERSION >= 19 */