Use context from root view to inflate children

- The display context doesn't copy the theme from the original,
  so we shouldn't use it to inflate other child views directly
- Revert previous temporary changes

Bug: 165014649
Test: atest -it android.server.wm.MultiDisplayKeyguardTests
Change-Id: Ifa55e2808a707e7b2127dc606564f338c809c960