insights: backend: possible double-inserts (over-reporting) if container restarts happen frequently

Created by: slimsag

This will need to be resolved in the job scheduler, we might record the same data point multiple times (and report the sum of them instead of e.g. average) if the container restarts multiple times, since recording happens on startup and then 12h after (instead of e.g. on every 12th hour)

https://github.com/sourcegraph/sourcegraph/pull/18506#discussion_r579459419