With a multiple database application `db:rollback` becomes problematic.
We can't rollback just the primary, that doesn't match the behavior in
the other tasks. We can't rollback a migration for every database, that
is unexpected.

To solve this I handled `db:rollback` the same way I handled `:up` and
`:down`. If `db:rollback` is called for a multi-db application then it
will raise an error recommending you use `db:rollback:[NAME]` instead.
Calling `db:rollback:primary` or `db:rollback:animals` will rollback
the migration for the number of steps specified.

Closes: #38513
Follow-up to: #34078