InlineEnclosure markup id could collide in the final page markup

WICKET-5085 introduced a 'counter' variable in InlineEnclosureHandler that should make the component id of the InlineEnclosure unique in its parent.
But the component id is also used as markup id and this leads to a problem when InlineEnclosure is used in different panel because a new instance of InlineenclosureHandler is used and its 'counter' value starts from 0 again.