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/recently_read_item.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
-<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
+<androidx.cardview.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
     android:id="@+id/cv_manga"
     style="@style/Theme.Widget.CardView.Item"
     android:padding="0dp">
@@ -69,4 +69,4 @@
                 android:text="@string/action_resume"/>
         </RelativeLayout>
     </LinearLayout>
-</android.support.v7.widget.CardView>
+</androidx.cardview.widget.CardView>