Remote repo: track repo owner

[stsewd]

What's the problem this feature will solve?

For repos that belong to an organization, we are tracking the organization in the RemoteRepository model, but for repos that belong to a user, we aren't tracking that information, we can infer the owner from the name (user/repo), but sometimes we may need more than the name, like the ID of the owner (this information would have been useful for migrating from our old GH OAuth app to our new GH App).

Describe the solution you'd like

Track the owner of the repo in a owner attribute, similar to organization, or check if it makes sense to merge both in one attribute like GH does. We should also check if the other providers share this same concept, I know that Gitlab has things like subgroups...

Alternative solutions

Just do nothing as this isn't required for anything else other than the migration to the new GH app.

Additional context

#12112 (comment)