[validator] throw an exception if isn't an instance of ConstraintValidatorInterface.
bug #9718 [validator] throw an exception if isn't an instance of ConstraintValidatorInterface. (aitboudad)

This PR was squashed before being merged into the 2.3 branch (closes #9718).

Discussion
----------

[validator] throw an exception if isn't an instance of ConstraintValidatorInterface.

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #9264
| License       | MIT

Commits
-------

fc232a5 [validator] throw an exception if isn't an instance of ConstraintValidatorInterface.