Create ThemeOverlayController in SystemUI.

This service runs as user 0 and applies the current users' theme
customization overlay settings to user 0, associated work profiles, and
user 0 for packages that affect systemui

Bug: 126238021
Bug: 124426955
Test: unit tests; switch to secondary user and guest user and change overlays
Change-Id: I35dd9113eab1b1c1cfc81f0b38aa04900fa740dd