optimize TS generated Model output

[manolo]

At some time we should remove unused imports from Binder and FormValidator among the ts-ignore comment.

// @ts-ignore
import {Binder, ObjectModel, AnyModel, StringModel, NumberModel, ArrayModel, BooleanModel, PrimitiveModel, Required} from '@vaadin/flow-frontend/Binder'
// @ts-ignore
import {Email,Null,NotNull,NotEmpty,NotBlank,AssertTrue,AssertFalse,Negative,NegativeOrZero,Positive,PositiveOrZero,Size,Past,PastOrPresent,Future,FutureOrPresent,Digits,Min,Max,Pattern,DecimalMin,DecimalMax} from '@vaadin/flow-frontend/FormValidator'