Improve debugging for multi-instance in split-screen

It’s helpful to have the lunch mode information for debugging the
multi-instance behavior in split-screen.

fixes: 247992106
Test: Check from logcat when start activity.
      e.g. ActivityTaskManager: START u0 {flg=0x10000000
      cmp=com.google.android.deskclock/com.android.deskclock.DeskClock
      (has extras)} with LAUNCH_SINGLE_TASK from uid 10169
Change-Id: I003f555bd29260654ebf92252b536ec13481ea17

services/core/java/com/android/server/wm/ActivityStarter.java

@@ -892,9 +892,10 @@ class ActivityStarter {
 
         final int userId = aInfo != null && aInfo.applicationInfo != null
                 ? UserHandle.getUserId(aInfo.applicationInfo.uid) : 0;
+        final int launchMode = aInfo != null ? aInfo.launchMode : 0;
         if (err == ActivityManager.START_SUCCESS) {
             Slog.i(TAG, "START u" + userId + " {" + intent.toShortString(true, true, true, false)
-                    + "} from uid " + callingUid);
+                    + "} with " + launchModeToString(launchMode) + " from uid " + callingUid);
         }
 
         ActivityRecord sourceRecord = null;