Make solid invocation directly call the underlying decorated fxn
Summary: This diff makes direct invocation call the underlying python function instead of the compute_fn.
Test Plan: Re-adjusted tests to account for new state of the world. Some tests exist to document that we don't catch incorrect behavior.
Reviewers: sandyryza, alangenfeld, owen
Reviewed By: alangenfeld
Differential Revision: https://dagster.phacility.com/D8275