Currently, SiteStats is entirely static (documented as Static accessor class for site_stats and related things) forcing it to retrieve dependencies from mediawiki services.
I propose that it be converted to a service, similar to how MWNamespace's static methods were converted to a NamespaceInfo service
Dependencies to be injected:
- DBLoadBalancer
- LoggerInstance (currently uses wfDebug)
- MainWANObjectCache
- JobQueueGroup
- the config value of MiserMode