Usage of `dynamic` in `WebAPI`

[xPaw]

The API allows doing stuff like this:

dynamic steamNews = WebAPI.GetInterface( "ISteamNews" )
steamNews.GetNewsForApp002( appid: 730, maxlength: 100, count: 5 );

I always found this odd however, but since we can't realistically generate API methods like protobufs, I'm not sure what's a better way of doing things here besides just using the CallAsync which accepts method as string and parameters as args object (which the dynamic object parses into anyway).

One way of fixing this could be creating a source generator which replicates this functionality but without usage of dynamic.

[xPaw]

I think I would go with removing dynamic support, but I'd like to support #1438 first, to make migrating for a lot of web apis nicer.

[JustArchi]

dynamic is evil, since there are no compile-time guarantees that you're even doing the right thing, i.e. using correct number of parameters and likewise.

I used it initially in ASF but quickly discovered how much of headaches it gives me, moved to CallAsync() soon enough.

Maybe obsoleting GetInterface for several versions first is a good idea.