Misc baseline support for SysUI.

SysUI code relies on the straightforward Singleton, DisplayInfo,
and PinResult 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: Iea091bb09f6df9f8b23593871a805646a215ac0a