[Blazor] Don't include blazor.web.js or blazor.server.js if the app doesn't reference Microsoft.AspNetCore.Components.Endpoints or Microsoft.AspNetCore.Components.Server

Right now, we include the files as assets when the app references one of the two. We should be able to determine when the app is referencing the `.Endpoints` and `.Components.Server` assemblies and only include the assets in those situations.

Start by locating the asset inclusion logic for blazor.web.js and blazor.server.js, then trace how assembly references are detected. Verify behavior for apps referencing Microsoft.AspNetCore.Components.Endpoints, Microsoft.AspNetCore.Components.Server, both, or neither; done means assets are included only for the applicable references.

Written by the indexing model from the issue text.