Implement a validation to avoid insert class inside of attribute fields since there is a class field

Problem/Motivation

There're class fields and there're attributes field as well. In order to have consistence and to be organized we need to avoid classes to be added in the attributes field since there're specific fields for that

Steps to reproduce

1. Go to the blocks settings page
2. Go to attributes
3. Insert attribute key as "class"
4. Insert any value
5. Save
6. Expected: The class is saved
7. Result: The class should be validated in the attributes since there are class fields

Proposed resolution

Implement a validation in the Helper Service and send a message saying this

Remaining tasks

User interface changes

API changes

Data model changes