Submit cloud jobs behind the Sematic API Server

[augray]

Right now when submitting k8s jobs, it happens from the clients (either from the resolver in detached mode, or from a user machine in non-detached mode). We should put this behind the API server. This will help make re-runs easier to implement, and also make it so that end-users don't have to install/set up k8s to execute in the cloud.