Runtime: Allow (enforce?) jobs to be lazily compiled to support Runs

Right now, when the runtime executes a workflow, it expects all the expressions (jobs) to be compiled.

The CLI will pre-compile all expressions and log about it before the runtime is invoked.

But Lightning has this notion of a Run, which is the execution of a single job within a workflow.

To properly interface with Lightning, we need compilation to run just before the expression is executed so that it can be associated with a run id. So the job starts, gets compiled, executes, and decides what to do next, all as part of a Run.

At the moment it's kind of impossible to reflect this organisation in the runtime because compilation happens before the job id is created.

This probably isn't necessary for release, but I do think it's really important to make compilation visible.

The solution I think is for the runtime to accept a compile hook, which calls out to whatever runtime manager is calling it. It probably makes sense for the CLI to use lazy compilation as well.

Start by tracing the runtime workflow execution path and the CLI's current pre-compilation flow. Review how a job id and Lightning Run are created, then determine the boundaries for a compile hook. Done means the runtime and CLI behavior support compilation immediately before execution and associate it with the Run.