Upgrade to Node 20 on CI, enable actions cancellation (#24524)

- Upgrade node, the
[snap](7abe958f5b/snap/snapcraft.yaml (L47))
is excluded from this because [there is no Node 20 snap
yet](https://snapcraft.io/node).
- Add actions build cancellation based on
[this](https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#example-using-a-fallback-value).

---------

Co-authored-by: techknowlogick <techknowlogick@gitea.io>

.github/workflows/pull-docker_dryrun.yml

@@ -2,6 +2,10 @@ name: "Pull: Docker Dry Run"
 
 on: [pull_request]
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
 jobs:
   docker_dryrun:
     runs-on: ubuntu-latest