[3/n] Move new picker logic to AOSP

HubFragment shows below sections for ThemePicker build.

- Wallpaper
- Dark/Light theme
- Themed icon
- Grid

Bug: 190354625
Test: Build and run the app
Change-Id: I5ab205f7f4dbf5838c39ca0eca4808cad3c86fa1
2 files changed