coqbot minimizer should upload and attach the file to GH when it's truncated

[JasonGross]

We can probably use actions/upload-artifact#50 / https://docs.github.com/en/free-pro-team@latest/rest/reference/actions#download-an-artifact to get a link to the uploaded artifact(s) from the GH Actions job, and include the URL in the data we send to the bot.

[JasonGross]

The bug minimizer runner will now include links directly to the artifacts like

<details><summary>Build Log (contains the Coq error message) (truncated to last 8.0KiB; full 12KiB file on <a href="https://github.com/coq-community/run-coq-bug-minimizer/actions/runs/7493577714">GitHub Actions Artifacts</a> under <a href="https://github.com/coq-community/run-coq-bug-minimizer/actions/runs/7493577714/artifacts/1163423296" api-href="https://api.github.com/repos/coq-community/run-coq-bug-minimizer/actions/artifacts/1163423296/zip"><code>build.log</code></a>)</summary>

So now I think it's up to the bot to look at the comment html for any a tags with api-href, download the artifact, upload it to the repo GitHub, and link to it in the comment. I guess the minimizer runner could plausibly do its own upload on its own repo, to persist the data past when logs expire, using https://github.com/j178/github-s3 ? see also coq/coq.github.io#234 (comment)