Use CustomizationPickerActivity as main activity

Screenshot: https://screenshot.googleplex.com/B76hYpdpftbooD4.png

Bug: 190354625
Test: m WallpaperPicker2
Change-Id: I04ca4ddb49d1cabc5e8e38a79be0e8043cd14c6d
diff --git a/Android.bp b/Android.bp
index 1776e05..871e193 100644
--- a/Android.bp
+++ b/Android.bp
@@ -82,6 +82,13 @@
        + "$(location soong_zip) -o $(out) -C $$RES_DIR -D $$RES_DIR"
 }
 
+filegroup {
+    name: "WallpaperPicker2_Manifest",
+    srcs: [
+        "AndroidManifest.xml",
+    ],
+}
+
 java_defaults {
     name: "WallpaperPicker2_defaults",