Deprecate internal_container_registry env var scope

[rocketeerbkw]

With the removal of harbor from Lagoon core, env vars with scope internal_container_registry are no longer used. We should deprecated it, possibly remove it.

At a minimum, we can remove all usage in resolvers and delete data in the api-db. Maybe we have to keep the enum value but we can return an error if we want to be super BC careful (not sure there's a valid reason though).

[shreddedbacon]

We can follow the same deprecation process we've done for other things. Announce the deprecation, then in a subsequent release remove it entirely.

Since the harbor core support is already gone, we can do this a bit differently but still follow the same thing.

• announce deprecation
• keep the enum
• remove data as required
• no-op api interactions

In a subsequent release

• remove the enum