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
diff --git a/src/com/android/launcher3/Launcher.java b/src/com/android/launcher3/Launcher.java
index 4f7380a..0e155a2 100644
--- a/src/com/android/launcher3/Launcher.java
+++ b/src/com/android/launcher3/Launcher.java
@@ -63,6 +63,8 @@
 import static com.android.launcher3.popup.SystemShortcut.WIDGETS;
 import static com.android.launcher3.states.RotationHelper.REQUEST_LOCK;
 import static com.android.launcher3.states.RotationHelper.REQUEST_NONE;
+import static com.android.launcher3.util.Executors.MAIN_EXECUTOR;
+import static com.android.launcher3.util.Executors.MODEL_EXECUTOR;
 import static com.android.launcher3.util.ItemInfoMatcher.forFolderMatch;
 
 import android.animation.Animator;
@@ -2475,6 +2477,12 @@
                             (FolderInfo) item);
                     break;
                 }
+                case LauncherSettings.Favorites.ITEM_TYPE_APP_PAIR: {
+                    FolderInfo info = (FolderInfo) item;
+                    // TODO (jeremysim b/274189428): Create app pair icon
+                    view = null;
+                    break;
+                }
                 case LauncherSettings.Favorites.ITEM_TYPE_APPWIDGET:
                 case LauncherSettings.Favorites.ITEM_TYPE_CUSTOM_APPWIDGET: {
                     view = inflateAppWidget((LauncherAppWidgetInfo) item);