Refactor startIntentAndTaskWithLegacyTransition

Param intentFirst is not necessary because we could use stagePosition
to ensure intent side is left or right.
Remove it and ensure start task on main stage at split side.

Bug: 218613028
Test: pass existing tests
Test: manual
Change-Id: I3b8fc74b18c4d48fe73b501be696c3d59677183b

quickstep/src/com/android/quickstep/util/SplitSelectStateController.java

@@ -156,9 +156,8 @@ public class SplitSelectStateController {
                         splitRatio, adapter);
             } else {
                 mSystemUiProxy.startIntentAndTaskWithLegacyTransition(taskPendingIntent,
-                        new Intent(), taskId2, stagePosition == STAGE_POSITION_TOP_OR_LEFT,
-                        mainOpts.toBundle(), null /* sideOptions */, STAGE_POSITION_BOTTOM_OR_RIGHT,
-                        splitRatio, adapter);
+                        new Intent(), taskId2, mainOpts.toBundle(), null /* sideOptions */,
+                        stagePosition, splitRatio, adapter);
             }
         }
     }