[feat] harnesses can accept cli args

[OwenPriceSkelly]

closes #49

Before, harnesses must have been zero-argument functions:

@hog.harness()
def main():
    result = process_data.remote("hardcoded-dataset")
    return result

But a common pattern in some of the typical target use-cases (i.e. "monster scripts" that are run and re-run on a remote cluster) is to make heavy use of CLI args. We now support the following:

@hog.harness()
def main(dataset: str, epochs: int = 10, debug: bool = False):
    result = train_model.remote(dataset, epochs, debug)
    return result

We don't do any of the signature inspection or parsing ourselves; since typer is already a dependency of ours, we just turn the harness into an ad-hoc typer app with a single command at runtime. This adds a little unavoidable complexity (we need to invoke_harness_with_args instead of just calling result = harness_func()), but since we're ultimately just plugging into the very battle-tested typer/click libraries I'm not worried.

As a bonus, power-users can also directly use typer.Option or typer.Arguments in their harnesses and it should "just work" the same as it would a vanilla typer app.