Add flag to load Cryptol module immediately when starting cryptol-remote-api

[atomb]

This makes the most common stateful operation happen immediately on startup so we can treat it as essentially a stateless service (for certain use cases). We could also create a different executable that supports this and doesn't support some of the potentially stateful methods.

[weaversa]

It might be helpful to have the default for the flag be to load the Cryptol prelude.