Make it possible to check processed DeviceConfig flags.

Make it possible to track the most recently processed DeviceConfig flags
and get the value that was processed to help deflake tests.

Bug: 271128261
Bug: 322031031
Bug: 322871938
Bug: 323084558
Bug: 323621598
Test: atest --rerun-until-failure 25 CtsJobSchedulerTestCases:FlexibilityConstraintTest
Change-Id: Iaec284b6670cef490a1ea93b5849fd5065cefe80