Add sharding key to raw_usage_data table for Cells 1.0 compliance

Problem

Parent issue #434997 (closed)

Currently the only table we use (raw_usage_data) doesn't have sharding key. In order to comply with Cells 1.0 we need to add the key to the table docs.

However, the table is not in use on Gitlab.com since we don't generate service ping here. The last record was a year ago.

Desired Outcome

Sharding key exists for the table

Potential Solution

There is a complany-wide issue to track migration to sharding keys #429184 (closed).

Documentation

Add organization_id to the table. Set the column value to Default organization for the existing rows (both SM and .com) and all the new records on SM.

Further actions needed

In the future we should consider moving ServicePing generation per organisation other than per instance