Fix themed settings icons.

- Added android prefix for homeAsUpIndicator attribute
- Override ic_arrow_down_24dp from androidx
- Remove ic_lock drawable overlay
- Update date and time icon
- Dedupe ic_menu_add and ic_add_24dp

Bug: 131346125
Test: mp settings;
Change-Id: I7223249f2adccc5569a37e8b68cae5499e7c7620

res/menu/vpn.xml

@@ -18,6 +18,6 @@
     <item
         android:id="@+id/vpn_create"
         android:title="@string/vpn_create"
-        android:icon="@drawable/ic_menu_add"
+        android:icon="@drawable/ic_add_24dp"
         android:showAsAction="always" />
 </menu>