Upgrade github action versions

[derrickaw]

1. upgrade upload_artifact version to v7
2. upgrade download_artifact version to v7
3. upgrade checkout version to v6
4. Addresses this warning:
   Node.js 20 actions are deprecated. The following actions are running on Node.js 20 and may not work as expected: actions/checkout@v4, actions/upload-artifact@v4. Actions will be forced to run with Node.js 24 by default starting June 2nd, 2026.

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[gemini-code-assist]

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[derrickaw]

Hi @Abacn, do the runner containers still run on node 20? or have they been upgraded to 24? Thanks.