Adjust how steps are displayed, to make the appearance cleaner and keep a focus on the DSL. Suggested changes:

• Make Snippet Generator list the StepDescriptor.functionName first, as a sort key, followed by the StepDescriptor.displayName. So for example, you might see a pulldown entry sh: run a Unix shell script.
• Change the console log to print just the functionName, not the displayName.
  • For steps which add LabelAction, like stage, follow the function name with the label: stage: Production. That probably means this call is no longer useful.
  • For block start/stop nodes, perhaps show something like node { or } // node.
  • Metasteps (checkout, step, wrap) need changes but this is covered by JENKINS-29922.
  • Ideally, use ConsoleNote to render metadata with special markup so it does not distract from build output.
• Tweak the display of Workflow Steps similarly. (FlowNode.getDisplayName might still be OK here if the implementation were modified somewhat.)