Add a Re-execute button to the pipeline run view
Summary: Refactors the pipeline run view a bit so that you can re-execute a single step or re-excute the entire pipeline using a button in the top of the log area.
Test Plan: Updated snapshot tests
Reviewers: schrockn, alangenfeld
Reviewed By: schrockn
Differential Revision: https://dagster.phacility.com/D513