Don't use WMS.mWindowMap to synchronize WM critical section (36/n)

Use new field WMS.mGlobalLock instead. This will make it easier to
switch the lock to the same object used by ActivityTaskManagerService
in an upcoming CL.

Test: Existing tests pass
Bug: 80414790
Change-Id: I4202e9028395d79cc60b01ed795528b469a16bf1
diff --git a/services/core/java/com/android/server/wm/TaskPositioner.java b/services/core/java/com/android/server/wm/TaskPositioner.java
index d2696c0..66ebc9b 100644
--- a/services/core/java/com/android/server/wm/TaskPositioner.java
+++ b/services/core/java/com/android/server/wm/TaskPositioner.java
@@ -159,7 +159,7 @@
                         if (DEBUG_TASK_POSITIONING){
                             Slog.w(TAG, "ACTION_MOVE @ {" + newX + ", " + newY + "}");
                         }
-                        synchronized (mService.mWindowMap) {
+                        synchronized (mService.mGlobalLock) {
                             mDragEnded = notifyMoveLocked(newX, newY);
                             mTask.getDimBounds(mTmpRect);
                         }
@@ -192,7 +192,7 @@
 
                 if (mDragEnded) {
                     final boolean wasResizing = mResizing;
-                    synchronized (mService.mWindowMap) {
+                    synchronized (mService.mGlobalLock) {
                         endDragLocked();
                         mTask.getDimBounds(mTmpRect);
                     }
@@ -397,7 +397,7 @@
         // bounds yet. This will guarantee that the app starts the backdrop renderer before
         // configuration changes which could cause an activity restart.
         if (mResizing) {
-            synchronized (mService.mWindowMap) {
+            synchronized (mService.mGlobalLock) {
                 notifyMoveLocked(startX, startY);
             }