Remove unneeded statusbar view references from StatusBar.java

- In two cases, the check for (mStatusBarView != null) was vestigial from
  when the shade shared a window with the status bar window.

- Removed an unused `getStatusBarView` method from ShadeControllerImpl

- Added a ConfigurationListener to PhoneStatusBarViewController so it
  could update its own resources instead of relying on statusbar for the
  callback

Test: atest SystemUITests
Bug: 209005990
Change-Id: I7c15ec862c75006d9992ea80037160b330d6d4ce