Restrict PrefetchDataService access to features

This change will ensure that features are not able to directly use
(or misuse) PrefetchDataService.

Bug: b/379628362
Test: atest FeatureManagerTest
Test: atest MapOfDeferredWithTimeoutTest
Flag: EXEMPT bug fix
Change-Id: I7c2319c35ce3987c7c1d18b2d881cd692a900b2a