Update workflows to only add a single comment for how to run an image

[TimHess]

See #48 for an example of excessive "how to run this image" comments

[bart-vmware]

One way to accomplish this is by using the GitHub CLI, such as here:

run: gh pr comment $PR_NUMBER --edit-last --create-if-none --body-file coveragereport/Summary.md
env:
  GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
  PR_NUMBER: ${{ github.event.number }}

[TimHess]

One way to accomplish this is by using the GitHub CLI, such as here:

run: gh pr comment $PR_NUMBER --edit-last --create-if-none --body-file coveragereport/Summary.md
env:
  GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
  PR_NUMBER: ${{ github.event.number }}

That seems like a simple solution, but there are up to 4 different workflows that might want to add a comment... quick experiment in #50 shows the comments overwrite each other. We could probably do some scripting to evaluate the comment body and append to it, but I wonder how annoying that race condition would be.