General: Review core validators and extension method validators (duplicated behaviour)

[deandreamatias]

Is there an existing issue for this?

• I have searched the existing issues

Package/Plugin version

11.0.0

What you'd like to happen

I think that some core validators could be accomplish with extension methods and viceversa. Maybe can remove some of them.

Alternatives you've considered

Example: skipWhen
I understand that `FormBuilderValidators.skipWhen(validator: FormBuilderValidators.numeric(), condition: (int? value) => value == 0)` is the same that `FormBuilderValidators.numeric().skipWhen(condition: (int? value) => value == 0)`

Aditional information

No response