Switch custom url scheme handlers to url loaders

We can no longer implement customer url schemes as job factories, they now have to be url loaders.

This can be setup two different ways. CEF and android webview, does in the proxying url-loader-factory that also handles intercepts. But they can also be added as urlloader factories in ContentBrowserClientQt::RegisterNonNetworkNavigationURLLoaderFactories and ContentBrowserClientQt::RegisterNonNetworkSubresourceURLLoaderFactories