Revert "Migrates full screen user switcher to use CarUserManagerHelper instead of"

This reverts commit d0e6eeeb8ceb6e06ed92c84e37ea0c80ab567947.

Reason for revert: broke AAAPlusPlusVerifySysuiRequiredTestPropertiesTest
Bug: 80150596
Bug: 112608847

Change-Id: I706768f7a95b079663fd2ac9a013ffb068c45f85
3 files changed