HHH-5946 Fix not equal operator on composite types (4.3).

Same as #792 but on branch 4.3. See [HHH-5946](https://hibernate.atlassian.net/browse/HHH-5946).

Comparison operator other than equality weren’t properly supported on composite types. We now support not-equal and throw a QuerySyntaxException when any other operator than equal or not-equal is used. Of course, we still support equality, tests have been added to check this.