Performance-friendly validation

[maRci002]

Use case

Currently FormzInput.isValid / FormzInput.isNotValid / FormzInput.error / FormzInput.displayError / FormzInput.validator / Formz .validate methods / getters always recalculate the error which is waste of cpu cycle.

FormzInput is @immutable abstract class and it's validator method should return same result no matter how many times called at any point in time (pure function) since the validation logic can be expensive for instance a long regexp.

Proposal

• Error should be calculated at construct time
• Error should be lazy calaculated