[Components] Prerrendering startup experience
* Introduces an IComponentPrerrenderer to handle Prerrendering
* MVC registers a basic static prerrrenderer.
* Components registers a more feature complete prerrender that will
handle reconnection to the original circuit after prerrendering in
the future to allow for prerrendered interactive components.
* Removes UseRazorComponents
* Removes the SPA fallback in favor of a catch all route in
Index.cshtml
* Moves the framework files to be served by the default StaticFiles
middleware in the pipeline by way of plugging specific providers
through options.
* Lifts UseSignalR(r => r.MapHub<ComponentHub>()) into startup and
replaces it with a shorthand for MapHub using endpoint routing.
* Adds extension methods to map components to selectors for a given
hub.
* Updates the razor component templates to include prerendering and use a razor page as the entry
point.
Javier Calvarro Nelson
Chris Ross
Pranav K
Nate McMaster