Extend MetricsFactory so it can log to different LogWriters

- Renamed MetricsFractory to MetricsFeatureProvider, and access it using
  FeatureFactory.
- Instead of containing exactly 1 logWriter, MetricsFeatureProvider now
  contain a list.
- Added OnAttach event in Lifecycle. This is needed when a mixin
  requires Context to initialize itself.
- Updated tests.

Bug: 29575437
Test: make RunSettingsRoboTests
Change-Id: I7cc1528b9a744cd40088701e2bd115f41a8bf744