Replacing IViewComponentHelper can unexpectedly break ViewComponent TagHelpers

[NTaylorMullen]

If a user replaces the IViewComponentHelper with something that is not IViewContextAware you will get an invalid cast exception at runtime when trying to invoke a ViewComponent TagHelper. We should try to cast the IViewComponentHelper to IViewContextAware and if it can't be cast throw an acceptable exception.

[dougbu]

@NTaylorMullen we use (helper as IViewContextAware)?.Contextualize(ViewContext) everywhere else. Why isn't that correct here? Why throw at all?

[NTaylorMullen]

Hmm. Odd we do that elsewhere. I feel like throwing to let the user know that their app is incorrectly configured would be better than silently failing.

[NTaylorMullen]

Talked offline. You're absolutely right. If a service doesn't need to be contextualized to work then there's no reason for us to throw.

[danroth27]

If a user is using a feature and the component being resolved needs to be ViewContext aware and it isn't then we should throw a reasonable exception.

[NTaylorMullen]

@danroth27 It's plausible that a user can create an IViewComponentHelper that does not require ViewContext.