codeintel: Fix error on worker reprocessing

Created by: efritz

Ignore unique constraint violations from writeData. This error occurring means that we've half-processed a record (we write to two different datastores, so it's possible to have lsif data but no completed metadata), but when we try to reprocess it we hit a duplicate data error from the lsifstore (which is the only part that previously succeeded).

Currently these records should only go into the errored state, which is why we haven't seen it before. We may introduce different error retry/resetting schemes, in which case this condition needs to not be a fatal error (otherwise all retries are destined to fail unconditionally).