CAY-2846 Modeler: Allow to disable some validation rules in the project

[m-dzianishchyts]

What does this PR do?

• Refactors current validators.
• Provides modeler module with ValidationExtension to load and save validation config.
• Allows to edit validation config in the modeler.

Here is an example of cayenne-project.xml with customized validation config:

<?xml version="1.0" encoding="utf-8"?>
<domain xmlns="http://cayenne.apache.org/schema/11/domain"
	 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	 xsi:schemaLocation="http://cayenne.apache.org/schema/11/domain https://cayenne.apache.org/schema/11/domain.xsd"
	 project-version="11">
	<!-- Some other configs... -->
	
	<validation xmlns="http://cayenne.apache.org/schema/11/validation">
		<exclude>OBJ_ATTRIBUTE_INVALID_MAPPING</exclude>
	</validation>
</domain>

Images of changes

Windows 11:

Testing

Tested validation config loading (b7f4cc9)