Add repo_to_index check for zoekt scheduling service

The scheduling service should look for pending and initializing repositories and create corresponding indexing tasks for each repository.

• A scope to Search::Zoekt::Repository should be added of pending that includes pending and initializing repos.
• The scheduling service should dispatch an event that includes these repositories. Note: the argument should be one repository to ensure de-duplication
• An EventStore worker should pick up the event and create an indexing task