feat: Block startup until route provider is healthy

[shilingwang]

Summary

setup_route_provider now waits until the route provider reports healthy before returning, ensuring downstream consumers always receive a fully initialized provider.

Health is polled every second using the existing RouteProviderWrapper::healthy() logic (at least one healthy node for dynamic providers; always passes for static RoundRobinRouteProvider).
A 2-minute timeout is enforced via tokio::time::timeout; if the provider has not become healthy within that window, the function returns an error.