Messaging: Use ActivityResultContracts for media and contacts

Instead of handling showing and picking the media ourselves,
use existing AcitivityResultContracts to pick images, videos
or contacts

Change-Id: I20079ad94882cc6bbfeae8d57ca0e4aa30612c01

Android.bp

@@ -59,6 +59,7 @@ android_app {
     defaults: ["messaging_defaults"],
 
     static_libs: [
+        "androidx.activity_activity",
         "androidx.annotation_annotation",
         "androidx.appcompat_appcompat",
         "androidx.collection_collection",