UserRecord support in user interactor.

This is needed for backwards-compatibility purposes. Classes that extend
BaseUserSwitcherAdapter deal in UserRecord data items and are too
numerous and too risky to refactor to use the newer UserModel and
UserActionModel.

As part of this work, this CL extracts shared logic to instantiate
UserRecord instances from UserSwitcherControllerOldImpl so it can be
reused by UserInteractor.

Bug: 246631653
Test: unit tests included. Manually verified old implementation still
works across status bar, quick settings, bouncer dropdown, and
full-screen user switcher.

Change-Id: I2214b26700a539551cae84eb71b7b90d2e785bef