Launch WallpaperPicker in a new task am: 8bed8d3454 am: d4ddbed638 am: 310b927d4a

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Settings/+/11862433

Change-Id: Iec864df0fa3c872e41d3ac4a2d0d1e20d9632dd7