[BOT.4] Make BpfCoordinator to support data warning

Invoke the existing polling thread to update data alert statistics.
Once the data alert limit has reached, trigger the notification.

Bug: 150736748
Test: BpfCoordinatorTest
Original-Change: https://android-review.googlesource.com/1302435
Merged-In: Ibf25560ca2e9f003d8eba01361dc7d35ec1b1627
Change-Id: Ibf25560ca2e9f003d8eba01361dc7d35ec1b1627