API to reload plugins

The feature would be a `Reload` API to be able to reload gRPC and Wasm plugins. I assume this can be done in two parts, because the problem domain is somehow different.

Wasm plugins can be reloaded by detecting binary changes on disk and then restarting the in-memory service. This would come with a new dependency like [fsnotify](https://github.com/fsnotify/fsnotify).

gRPC plugins would have to re-establish the connection to the server, probably by dropping active client connections.

Thoughts?