Refactor advanced task args argument validators

[bomoko]

This provides a (hopefully) better and simpler abstraction for validating advanced task definition arguments.

The function getAdvancedTaskArgumentValidator(sqlClientPool, environment, taskArguments) is a scaffolding function that returns an instance of the class AdvancedTaskArgumentValidator, into which it injects everything that's needed to validate incoming argument values for the given task arguments (given via the taskArguments parameter).

This change serves two purposes

1. It gets rid of the somewhat confusing advancedTaskDefinitionTypeFactory and tries to provide better encapsulation of the validation functionality.
2. Introduces some basic testing for the argument validators
3. By keeping DB calls in the getAdvancedTaskArgumentValidator function, we remove any dependencies that were inside the validators themselves (the environment validators were doing DB calls), opting to instead inject them.

General Checklist

• Affected Issues have been mentioned in the Closing issues section
• Documentation has been written/updated
• PR title is ready for inclusion in changelog

[bomoko]

Converting to draft - there's a logic issue when this isn't attached directly to an environment.