* Move startup action config into AddServerSideBlazor, so that UseServerSideBlazor is reduced to trivial shorthand that can become optional
* Make BlazorHub public so developers can use it with UseAzureSignalR
* Move BlazorHub to Microsoft.AspNetCore.Blazor.Server namespace for easier consumption
* Add notes
* Have E2E tests validate that devs don't have to call UseServerSideBlazor
* Add forgotten tweak
* CR: Document that BlazorHub methods are not intended for application use.
* CR: Rename extension method to UseSignalRWithBlazorHub
* CR: TryAdd
Steve Sanderson