Baseline PM flags and UserInfo for SysUI.

SysUI code relies on the straightforward Flags and UserInfo classes,
and working around them in SysUI would be quite disruptive, so this
change supports them under Ravenwood, along with tests to confirm
their behavior.

Bug: 319647875
Test: atest FrameworksCoreTestsRavenwood
Change-Id: I9f8bcf711a39b15a9aff457a8afe2a601e64eafd