[AF07] Make subclass of NetworkStatsService#Dependencies in the tests

This is a no-op refactoring that make a subclass of
NetworkStatsService#Dependencies in order to make the
follow-up changes can implement private getters in the
class and easier to review.

Test: TH
Bug: 313841499
Change-Id: If0de525b32abb9ad715c633f42b3c65c0d720d24