POM: The Producer model should declare `validation-api` as a runtime dependency

[wajda]

Producer model uses ValidationUtils class form the Spline Commons module that in turn optionally depends on Jakarta validation API. Modules that refer Producer API but not Validation API compile, but fail at runtime with:

Exception in thread "main" java.lang.NoClassDefFoundError: jakarta/validation/ConstraintViolationException
	at za.co.absa.spline.producer.model.v1_2.Operations.<init>(executionPlan.scala:63)
        ...
Caused by: java.lang.ClassNotFoundException: jakarta.validation.ConstraintViolationException
	at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:581)
	at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178)
	at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:522)
	... 5 more