[migration] make sure the repo knows about all constraint types Adding new constraint types is cumbersome. It's easy to forget to do it in a migration script. So sync the constraint types at the beginning of each migration. Closes #3724892

[migration] stop caching the mapping from constraint type name to eid It's not so frequent that a cache seems necessary, and we were not invalidating that cache when adding a new constraint type. Related to #3724892.