Add scrollbar for pool selection list

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

@@ -47,6 +47,8 @@
         android:layout_width="0dp"
         android:layout_height="0dp"
         android:layout_marginStart="8dp"
+        android:scrollbars="vertical"
+        android:scrollbarAlwaysDrawVerticalTrack="true"
         android:layout_marginTop="16dp"
         android:layout_marginEnd="8dp"
         app:layout_constraintBottom_toBottomOf="parent"