Migrate to AndroidX (#2424)

* Migrate to AndroidX (automatic conversion by Android Studio)

* AndroidX dependency code updates

* Fix source preference reparenting

* fixes the androidx prefererences icon spacing issue

(cherry picked from commit b76a15d960ec2cdf771be16377db0348b66b3179)

* Fix source preference screen heading size/list padding

Co-authored-by: Carlos <cargo8005@gmail.com>

app/src/main/res/layout/extension_detail_controller.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
-<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
@@ -73,7 +73,7 @@
         app:layout_constraintRight_toRightOf="parent"
         app:layout_constraintTop_toBottomOf="@id/extension_pkg" />
 
-    <android.support.v7.widget.RecyclerView
+    <androidx.recyclerview.widget.RecyclerView
         android:id="@+id/extension_prefs_recycler"
         android:layout_width="0dp"
         android:layout_height="0dp"
@@ -94,11 +94,11 @@
         app:layout_constraintRight_toRightOf="parent"
         app:layout_constraintTop_toBottomOf="@id/extension_uninstall_button"/>
 
-    <android.support.constraint.Guideline
+    <androidx.constraintlayout.widget.Guideline
         android:id="@+id/guideline"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:orientation="vertical"
         app:layout_constraintGuide_percent="0.5" />
 
-</android.support.constraint.ConstraintLayout>
+</androidx.constraintlayout.widget.ConstraintLayout>