Add method to determine if launcher is in split selection state

* Available for both launcher and taskbar via
ActivityContext

Bug: 295981634
Change-Id: I8767deea0b2432da3047209037874c966b83c3b3
diff --git a/src/com/android/launcher3/Launcher.java b/src/com/android/launcher3/Launcher.java
index 2b433f1..b34a527 100644
--- a/src/com/android/launcher3/Launcher.java
+++ b/src/com/android/launcher3/Launcher.java
@@ -3103,7 +3103,7 @@
     }
 
     /** To be overridden by subclasses */
-    protected boolean isSplitSelectionEnabled() {
+    public boolean isSplitSelectionEnabled() {
         // Overridden
         return false;
     }