[IntrusionDetection] Refactor the NetworkLogSource to register

callbacks directly to the system service.

Callback may only be created from the system service, so ignoring
unit tests without system service permissions for now.

DataAggregator initialize() is no longer called by the system service,
so added a check in enable().

Bug: 369313906
Test: atest IntrusionDetectionServiceTests
Flag: android.security.afl_api
Change-Id: I6140133a072242ea965ff55e1781074543b4dccb