Migrate all foreign keys to `bigint` from `integer`

I had missed this one in 63d85933ac99453c76df7cda102a4f60d94f5f53.
Thanks a lot to Robert for scouring the fields and finding it.

Since the v2 migration was irreversible, add a new one to change the
type of this foreign key.

Refs #4947

All our primary keys are supposed to be `bigint`s, and our foreign keys
should likewise be `bigint`s. But it's easy to forget this when creating
migrations, or some committers might not have been up to speed on the
convention. In any case, this changes all existing foreign keys to be
`bigint`s.

Need to get this out now so that Michel Etienne can use it to correctly
test the Java application for compliance check validations. That's why
I'm not including any future-looking checks or enforcements here. That
will be coming next.

Refs #4947