Logging: HomepageModule events
- Renamed Start module's tasks with 'start-' prefix
- New logger specifically for the HomepageModule schema
- Add wgGEHomepageLoggingEnabled to enable/disable logging specifically for the homepage feature
- Log impression, link-click, hover-in, hover-out
- Let modules override getState() so it gets included in action_data.
Bug: T219583
Change-Id: I0476cf8893711a6594af4f47859eb1df900f71d9