Insights: added commit index table and background job
Created by: coury-clark
Referencing #21784 (closed)
This PR adds
- A new set of tables to the code insights database that will act as an index of commits for the purposes of compressing the search queries required to generate an insight data series.
- A background job that will index repositories installed on the Sourcegraph instance and keep that index up to date. This job will only run if code insights is enabled (all of these insights jobs are migrating soon to the worker service as a dx project).