Cache power whitelisted apps.

DeviceIdleController sits higher in the lock hierarchy than
AppStandbyController, so ASC shouldn't call out to DIC with its lock
held. In order to know if an app is power whitelisted, ASC needs to call
out to DIC and cache the result outside of holding the lock.

Bug: 158779091
Test: atest CtsBatterySavingTestCases
Test: atest CtsJobSchedulerTestCases
Test: atest CtsUsageStatsTestCases:UsageStatsTest
Test: atest FrameworksServicesTests:AppIdleHistoryTests
Test: atest FrameworksServicesTests:AppStandbyControllerTests
Change-Id: Iff500f3ab00f6881348926604be7ab07693bdf40