Refactor grid migration

In this CL:
-Make GridsizeMigrationLogic functions pure (no side effects)
-Make it so GridSizeMigrationLogic contains the migration logic and does NOT interact with the database
-Let GridSizeMigrationUtil receive the results from the logic layer and use those results to interact with the database appropriately

In future CLs:
-Refactor GridSizeMigrationLogic to Kotlin

Bug: 358399271
Flag: com.android.launcher3.grid_migration_refactor
Test: GridSizeMigrationTest
Change-Id: Ifcc5ca356558a7463352580f2e89eef8c86ed16b

src/com/android/launcher3/model/LoaderTask.java

@@ -435,7 +435,15 @@ public class LoaderTask implements Runnable {
         final WidgetInflater widgetInflater = new WidgetInflater(context);
 
         ModelDbController dbController = mApp.getModel().getModelDbController();
-        dbController.tryMigrateDB(restoreEventLogger);
+        if (Flags.gridMigrationRefactor()) {
+            try {
+                dbController.attemptMigrateDb(restoreEventLogger);
+            } catch (Exception e) {
+                FileLog.e(TAG, "Failed to migrate grid", e);
+            }
+        } else {
+            dbController.tryMigrateDB(restoreEventLogger);
+        }
         Log.d(TAG, "loadWorkspace: loading default favorites");
         dbController.loadDefaultFavoritesIfNecessary();