Update UserInfoHelper and add Injector

Update UserInfoHelper to use Lifecycle methods for listening to user
changes, which are more timely and accurate than intent broadcasts. This
will eliminate edge case bugs around work profile handling.

Also creates an injection framework for location classes that can be
used by unit tests, and moves those classes into a util package.

Test: manual + presubmits
Change-Id: I86db218666a5e79df1283dd9dc4dfea3b65f86b9