Use project_id_from and project_id_to in the InitialIndexingEventWorker

What does this MR do and why?

Start using project_id_from and project_id_to to avoid trying to create the zoekt_repository for all the projects on each iteration of an index of a namespace having multiple indices. If there is no metadata about the project ranges then behave as it was doing previously. If there is only project_id_from then create the zoekt_repository from project_id_from and if there are both project_id_from and project_id_to then create zoekt_repository for the range of projects id (from..to) that belongs to the indexed namespace.

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Related to #509600 (closed)