[4/4] Move new picker logic to AOSP

- Remove activity overriden for CustomizationPickerActivity, and use
the activity in WallpaperPicker2.

Bug: 190354625
Test: Build and run the app
Change-Id: I080737f0ec30a6090b1180eba98b3aa8087f50a1
Merged-In: I080737f0ec30a6090b1180eba98b3aa8087f50a1
9 files changed