Improve Trunk's whole CI setup

[dnaka91]

trafficstars

• Update GitHub Actions and Zola to latest version
• Simplify (and parallelize) build of examples in CI
• Use action for CI cache, removed redundant steps
• Move away from the actions-rs GitHub Actions

Checklist

• [ ] Updated CHANGELOG.md describing pertinent changes.
• [ ] Updated README.md with pertinent info (may not always apply).
• [ ] Updated site content with pertinent info (may not always apply).
• [ ] Squash down commits to one or two logical commits which clearly describe the work you've done. If you don't, then Dodd will 🤓.

[dnaka91]

Let me just have a quick look again. Has been a while since I touched it.