Reject scalar Normalizer inputs (#32161)
This pull request improves input validation for the `Normalizer`
operator by adding a check to reject scalar (rank-0) inputs and
introducing a corresponding unit test to ensure this behavior. The main
changes are as follows:
**Input validation improvements:**
* Added a check in `normalizer.cc` to return an error if the input
tensor has rank 0, ensuring only rank 1 or 2 inputs are accepted.
**Testing enhancements:**
* Added a new test case in `normalizer_test.cc` (`ScalarInputRejected`)
to verify that scalar inputs are correctly rejected with an appropriate
error message.
