Rename `canvas-node` repo to `canvas`

[cmichi]

After this PR is merged I'll rename the repo.

I'll subsequently create follow-ups for:

• The CI team, so that they adapt GitLab.
• All other repositories which somehow use canvas-node (ink-waterfall, etc.).
• The Dockerfiles which reference this repo.

There will necessarily be a (hopefully short) timeframe when the CI for this project and once which depend on it won't work.

If everything works again I'll announce in our public channels that we've renamed the repo.