Add support for AndroidX preferences (#1971)

* Add stubs for AndroidX preferences

* Update extensions for AndroidX preferences

lib/preference-stub/src/main/java/androidx/preference/EditTextPreference.java

@@ -0,0 +1,19 @@
+package androidx.preference;
+
+import android.content.Context;
+
+public class EditTextPreference extends DialogPreference {
+
+    public EditTextPreference(Context context) {
+        throw new RuntimeException("Stub!");
+    }
+
+    public String getText() {
+        throw new RuntimeException("Stub!");
+    }
+
+    public void setText(String text) {
+        throw new RuntimeException("Stub!");
+    }
+
+}