Add location to dream overlay status bar.

This changelist adds a location icon to the dream overlay status bar
when location services are active.

Test: atest AmbientStatusBarViewControllerTest#testLocationIconShownWhenLocationActive
Test: atest AmbientStatusBarViewControllerTest#testLocationIconNotShownForOtherPrivacyItems
Test: atest AmbientStatusBarViewControllerTest#testLocationIconNotShownForNoItems
Fixes: 354688091
Flag: EXEMPT bugfix
Change-Id: I794a31ebce58a9d411de2b3a9e7687ed9174f24b