Add Split button in OverviewActions

Shows up only for large screen devices, not phones.
Tested for NexusLauncher, general 3P launcher support
needed for staged split (TODO b/195607777)

Bug: 195423591
Change-Id: I4d455769b17637174b590c640516b9fbb6352c3d

quickstep/src/com/android/quickstep/views/LauncherRecentsView.java

@@ -245,8 +245,8 @@ public class LauncherRecentsView extends RecentsView<BaseQuickstepLauncher, Laun
 
     @Override
     public void initiateSplitSelect(TaskView taskView,
-            SplitConfigurationOptions.SplitPositionOption splitPositionOption) {
-        super.initiateSplitSelect(taskView, splitPositionOption);
+            @SplitConfigurationOptions.StagePosition int stagePosition) {
+        super.initiateSplitSelect(taskView, stagePosition);
         mActivity.getStateManager().goToState(LauncherState.OVERVIEW_SPLIT_SELECT);
     }