Make WallpaperMS bind wallpaper component PendingIntent immutable. am: b392903052 am: f75396d3c6 am: 286aa8b9b4

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/12718696

Change-Id: I458eff483892bb657dffa854c56a25ab694e38ac