[SP02] Add provider interfaces to system API

This change contains a base class that allows external modules
to implement a custom network statistics provider. And a callback
interface that allows the implementation to signal the system.

These interfaces will be used in the follow-up changes that
implement the functionality.

Test: atest FrameworksNetTests CtsUsageStatsTestCases
Test: m doc-comment-check-docs
Bug: 130855321
Change-Id: Ib23377c8b9cef02bc32253462b068fd10734d21a
2 files changed
tree: 3a08e932f1f563e211f95cda67b41f11551b3e72
  1. core/
  2. packages/
  3. services/
  4. wifi/