When rebuilding group indexes from alter, don't include foreign keys

This is a temporary AIS subgraph that only needs to get proxies for the group indexes. It doesn't need the foreign keys, for which it would need to referenced table, too.

Rebuilding group indexes when adding a foreign key isn't needed. But this same code path is also followed when renaming a column for instance, so I don't think that's a particular shortcoming of foreign keys.

Includes the original report as a YAML test.