Use Node.js versions 18.x and 20.x for workflows (and needed modifications)

[marcjansen]

This PR updates the versions of Node.js used during CI runs.

This needed several iterations, until CI was successful:

• the OS dependencies of canvas needed to be adjusted
• I also used more recent versions of the actions, technically they are most likely not needed

The above was enough to get CI working in Node.js v18.x, but for Node.js v20.x. I also had to update the actual canvas versions, see also the release notes here, this is the first version witzh prebuilds for Node.js v20.x

tl;dr: this includes more than the title suggests, please review.

[KaiVolland]

I'd prefere to have the npm ci back again as it should be safer.

[marcjansen]

OK, will add another commit

[marcjansen]

@KaiVolland switched back. please have another look.

[KaiVolland]

Thanks!