`validate: false` is always appended to schema dumps

All of these tests are failing:

- test_dump_foreign_key_targeting_different_schema
- test_schema_dumping
- test_schema_dumping_on_delete_and_on_update_options
- test_schema_dumping_with_validate_false
- test_schema_dumping_with_validate_true
- test_schema_dumping_with_custom_fk_ignore_pattern

I haven't verified for all of them, but for most the bug is actually that the fk is not validated. This likely comes from :

https://github.com/cockroachdb/cockroach/blob/bfd7d1dfd002cf8b7d504d9732e2ae494c1abb9b/pkg/sql/backfill.go#L2593-L2605

> We can't support adding a validated foreign key constraint in the same
> transaction as the CREATE TABLE statement. This would require adding
> the backreference to the other table and then validating the constraint
> for whatever rows were inserted into the referencing table in this
> transaction, which requires multiple schema changer states across
> multiple transactions.
>
> We could partially fix this by queuing a validation job to run post-
> transaction. Better yet would be to absorb this into the transactional
> schema change framework eventually.
>
> For now, just always add the FK as unvalidated.
> ```go
> fk.ForeignKeyDesc().Validity = descpb.ConstraintValidity_Unvalidated