ci/cd: bump Node.js environment to 20.x

This commit upgrades Node.js version to v20.x in CI/CD environment.

Previously used Node 18.x is moving towards end-of-life, with a planned
date of 2025-04-30. In contrast, Node 20.x has been offering long-term
support (LTS) since 2023-10-24. This makes Node 20.x a stable and
recommended version for production environments.

This commit also configures `actions/setup-node` with the
`check-latest` flag to always use the latest Node 20.x version, keeping
CI/CD setup up-to-date with minimal maintenance.
Details:
- actions/setup-node#165
- actions/setup-node#160

Using Node 20.x in CI/CD environments provides better compatibility with
Electron v29.0 which moves to Node 20.x.
Details:
- electron/electron#40343

This upgrade improves network connection handling in CI/CD pipelines
(where issues occur due to GitHub runners not supporting IPv6).
Details:
- actions/runner#3138
- actions/runner-images#668
- actions/runner#3213
- actions/runner-images#9540

Node 20.x adopts the Happy Eyeballs algorithm for improved IPv6
connectivity.
- nodejs/node#40702
- nodejs/node#41625
- nodejs/node#44731

This mitigates issues like `UND_ERR_CONNECT_TIMEOUT` and localhost DNS
resolution in CI/CD environments:
Details:
- nodejs/node#40537
- actions/runner#3213
- actions/runner-images#9540

Node 20 introduces `setDefaultAutoSelectFamily`, a global function from
Node 19.4.0, enabling better IPv4 support, especially in environments
with limited or problematic IPv6 support.
Details:
- nodejs/node#45777

Node 20.x defaults to the new `autoSelectFamily`, improving network
connection reliability in GitHub runners lacking full IPv6 support.
Details:
- nodejs/node#46790

.github/actions/setup-node/action.yml

@@ -5,4 +5,5 @@ runs:
       name: Setup node
       uses: actions/setup-node@v4
       with:
-        node-version: 18.x
+        node-version: 20.x
+        check-latest: true