[Central Surfaces] Make shade privacy chip & status icons singletons.

Adding the `@Named` to `HeaderPrivacyIconsController` isn't strictly
necessary, but it makes those views consistent with the battery views
and ensures that the correct views are being passed in.

Bug: 277762009
Test: privacy chip and status icons work correctly in the shade
Change-Id: I424f96e232936346ca9c5b98e76b2b8f4de369af