Move LauncherWidgetHolder to widget package

Making LauncherAppWidgetHost package-private as well

Bug: 235358918
Test: N/A
Change-Id: If022ec8d429579a972991872b2dc11db76719341
diff --git a/src/com/android/launcher3/LauncherProvider.java b/src/com/android/launcher3/LauncherProvider.java
index a6731a5..457e126 100644
--- a/src/com/android/launcher3/LauncherProvider.java
+++ b/src/com/android/launcher3/LauncherProvider.java
@@ -71,6 +71,7 @@
 import com.android.launcher3.util.NoLocaleSQLiteHelper;
 import com.android.launcher3.util.PackageManagerHelper;
 import com.android.launcher3.util.Thunk;
+import com.android.launcher3.widget.LauncherWidgetHolder;
 
 import org.xmlpull.v1.XmlPullParser;