Sets up HttpClient with cngxAsyncInterceptor so every request
surfaces in CngxAsyncRegistry. Opt-in - add it to
bootstrapApplication providers alongside provideAsyncRegistry().
Use this only when cngx owns the HttpClient setup. It calls
provideHttpClient(withInterceptors([cngxAsyncInterceptor])) internally, so
an app that already calls provideHttpClient (especially with withFetch()
or other features) would get a second, feature-less HttpClient
configuration - last-provider-wins on HttpBackend can silently revert
withFetch() to the XHR backend. In that case do not call this; add the
exported cngxAsyncInterceptor to your own withInterceptors instead: