Update tile summary from ContentProvider.

A subscription is created and destroyed based on the lifecycle events.
Fetching the summary is done asynchronously to prevent blocking the UI
thread.

Test: make RunSettingsRoboTests
Test: manually flip flags, confirm tile has dynamic summary
Bug: 264812018
Change-Id: Ib1149ec6907b6a70226c36d37431023aaf6ad557
6 files changed