LSW: Properly set page transition and cleanup definitions on the way

Set slide animation by default and use it in all pages.
Fix wrong/missing slide animations on various transitions like WiFi
and the backup subpage.

Change-Id: I78c87f38eb615379d39c89b43a016ed2ffb98695

src/org/lineageos/setupwizard/WelcomeActivity.java

@@ -1,6 +1,6 @@
 /*
  * Copyright (C) 2016 The CyanogenMod Project
- * Copyright (C) 2017 The LineageOS Project
+ * Copyright (C) 2017-2018,2020 The LineageOS Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -52,11 +52,6 @@ public class WelcomeActivity extends BaseSetupWizardActivity {
         startEmergencyDialer();
     }
 
-    @Override
-    protected int getTransition() {
-        return TRANSITION_ID_SLIDE;
-    }
-
     @Override
     protected int getLayoutResId() {
         return R.layout.welcome_activity;