Publish RabbitMQ-Stream dashboard to grafana.com

[gerhard]

• Removed the Dockerfile
• Slimmed down the Makefile

All of this is now handled by https://github.com/rabbitmq/rabbitmq-server/blob/master/.github/workflows/oci.yaml
cc @Zerpet @pjk25

More details here (including the steps used to publish to grafana.com): https://github.com/rabbitmq/release-engineering/issues/11#issuecomment-887627938

I don't want to hold up this PR, will invest in automating the steps described in the previous link another time.

[ansd]

Thanks a lot @gerhard! Looks good!

I pushed one commit since make overview was failing for me.

I also left one in-line comment since the stream metrics don't show up for me in the Grafana dashboards when running make overview metrics.

[gerhard]

I'm trying out https://github.com/tibdex/backport for the first time. Let's see how well it works @pjk25 😉

[github-actions]

The backport to v3.9.x failed:

The process '/usr/bin/git' failed with exit code 128

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-v3.9.x v3.9.x
# Navigate to the new working tree
cd .worktrees/backport-v3.9.x
# Create a new branch
git switch --create backport-3250-to-v3.9.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick --mainline 1 ee6aa3067e96632d9801e64b6c3f5a3eebf9a7da
# Push it to GitHub
git push --set-upstream origin backport-3250-to-v3.9.x
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-v3.9.x

Then, create a pull request where the base branch is v3.9.x and the compare/head branch is backport-3250-to-v3.9.x.

[gerhard]

I'm not sure why the above backport failed. I could do the cherry-pick locally with no issues. The focus is on producing 3.9.1, so I'll stick with that and maybe come back to this later. For now I did a manual backport to v3.9.x, as per usual.

[HoloRin]

It looks like the backport action might just be broken. Rather than spend much time investigating I'm tempted to give https://mergify.io/features/backports a try. I will reconfigure things when I have a chance.