Handle config override via settings correctly

Initialize persistence only after we can read the settings
provider as we need to take into account the current config
potentially set as an override in settings vs using the
hard coded defaults.

Make the last persist time more robust to ensure it always
termines to guard against other unforeseen cases wehere the
persistet files don't match what is expected under the current
config.

Test: atest CtsAppOpsTestCases
Test: atest android.appsecurity.cts.AppOpsTest

Bug: 134093967

Change-Id: If7044c83268560972a8112a6fbf853cdd61a55b3