Add a native service to provide a random data source

[marceline-cramer]

Let's add a new plugin and associated service, named something like hearth-rand or hearth-rng, to provide cryptographically secure random data from the host.

I figure that the service could just be as simple as the request data being an integer, and the response being a vector of cryptographically random data sourced from the rand crate that is as long as the request's value.