feat: make pr_watcher success/failure comments more compact

Description

When open-craft-grove leaves a PR comment indicating that a sandbox either deployed or failed to deploy, it takes up too much vertical space on the PR. This PR uses markdown's link syntax in order to shrink the comment while still retaining all the information. It also adds some emojis.

This MR also includes a minor bugfix: Previously, when any of the info files (grove config, tutor config, or tutor requirements) failed to upload to DigitalOcean, Grove would leave all links out of the comment. This PR changes it so that only the missing links are left out of the comment.

Supporting information

Gábor and I agreed on this change in Slack.

Testing instructions

I'm not sure how to test this.

Dependencies

None, as far as I know.

Screenshots

Before:

After (manually edited):

Checklist

If any of the items below is not applicable, do not remove them, but put a check in it.

• All providers include the new feature/change
• All affected providers can provision new clusters
• Unit tests are added/updated
• Documentation is added/updated
• The TOOLS_CONTAINER_IMAGE_VERSION in ci_vars.yml is updated
• The grove-template repository is updated

Additional context

I couldn't figure out how to run linting or unit tests locally, so there could be an error in here.