Add actionlint to testing pipelines

[wren]

This PR adds actionlint to the testing pipelines. This will allow us to test changes to Github Actions before they are committed into the develop branch, and will alert us about common problems much sooner. It also fixes all linting issues currently in the pipeline files so that we don't have a bunch of warnings right from the start.

I also recommend actionlint to anyone working on Github Actions (it's a very useful tool).

Checklist

• I have read the contributing doc.
• I have included a link to the relevant issue number.
• I have checked to ensure there aren't other open pull requests
  for the same issue.
• I have written new tests for these changes, as needed.