[Blazor] Unify root components initialization paths.

When we initialize components (specially in Blazor Server) we have since 8.0 three different ways in which components get initialized.

* First through `ComponentHub.Start` for old `blazor.server.js`.
* Second through `UpdateRootComponents` by `blazor.web.js`.
* Third through JS Root components via `CircuitJSComponentInterop.cs`.

This is problematic because it creates slight variations of our initialization logic that manifest themselves in bugs that are hard to track.

We should consider standarizing on `UpdateRootComponents` since that's the model Blazor Web uses. This would involve:
* Update `blazor.server.js` to go through UpdateRootComponents (same as blazor.web.js).
* This would mean we could get rid of the old `blazor.server.js` initialization code, as it would be handled by `blazor.web.js`.
* Update JS root components to also go through `UpdateRootComponents`.
* We would get rid of the JS interop associated with this functionality as it would be subsumed by UpdateRootComponents.
* We would likely require expanding the RootComponentDescriptors to accept creating components with "client descriptors" which would be subject to the same restrictions JS Root Components have today.