Make __vanish__ part of the public API

[joeldrapper]

Discussed in https://github.com/orgs/phlex-ruby/discussions/583

^{Originally posted by bradgessler July 21, 2023}
Sometimes a component needs to be rendered, but the output is not needed, like in this controller at https://github.com/rubymonolith/classic/blob/47d9fee6e17f5f49d7dfbefee4b194b6eddcff8d/app/controllers/posts_controller.rb#L71-L73 so Superform can permit params based on the contents of a form.

Could this __vanish__ API be made available for such calls? I see I can include DeferredRender to enable that, but I only need this for permitting params. When I'm actually rendering the form in a view I don't need to defer rendering.