App Pairs (behind flag): Add new ItemInfo types and DB save functionality

This is the second of several patches implementing the App Pairs feature behind a flag.

This patch includes:
- AppPairsController, a new controller that will handle creation, launching, and deletion of app pairs
- ITEM_TYPE_APP_PAIR is a new type of FolderInfo (FolderInfo now can be either a folder or an app pair, and should probably be renamed to CollectionInfo or something more generic in future)
- Necessary plumbing for these new types
- Database code that handles saving a new app pair to the database with the correct schema

Flag: ENABLE_APP_PAIRS (set to false)
Bug: 274189428
Test: Not included in this CL, but will follow
Change-Id: Ie3aefd4eb9171f471789f54876de742849d3013b

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

@@ -84,6 +84,7 @@ public class SplitSelectStateController {
     private final Handler mHandler;
     private final RecentsModel mRecentTasksModel;
     private final SplitAnimationController mSplitAnimationController;
+    private final AppPairsController mAppPairsController;
     private StatsLogManager mStatsLogManager;
     private final SystemUiProxy mSystemUiProxy;
     private final StateManager mStateManager;
@@ -128,6 +129,7 @@ public class SplitSelectStateController {
         mDepthController = depthController;
         mRecentTasksModel = recentsModel;
         mSplitAnimationController = new SplitAnimationController(this);
+        mAppPairsController = new AppPairsController(context, this);
     }
 
     /**
@@ -586,4 +588,8 @@ public class SplitSelectStateController {
     public FloatingTaskView getFirstFloatingTaskView() {
         return mFirstFloatingTaskView;
     }
+
+    public AppPairsController getAppPairsController() {
+        return mAppPairsController;
+    }
 }