Update LabelAction messages for Build and WaitForBuild steps

[stuartrowe]

The label for the build step should differentiate between whether the step is waiting for the scheduled build to complete. Similarly the waitForBuild step label should reference the build it's waiting on.

Testing done

Ran local pipelines that called build with a combination of wait=true, wait=false and waitForStart=true along with calling the waitForBuild step. Confirmed that labels associated with the step nodes was updated accordingly.

Submitter checklist

• Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
• Ensure that the pull request title represents the desired changelog entry
• Please describe what you did
• Link to relevant issues in GitHub or Jira
• Link to relevant pull requests, esp. upstream and downstream changes
• Ensure you have provided tests - that demonstrates feature works or fixes the issue

[stuartrowe]

@jglick please take a look/tag appropriate reviewers.