ci: use self-hosted runner for building docker containers

[yzh119]

📌 Description

Github default runner's disk space is too small and results in OOM issues: https://github.com/flashinfer-ai/flashinfer/actions/runs/18389642821/job/52402828516

🔍 Related Issues

#1901

🚀 Pull Request Checklist

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🧪 Tests

• Tests have been added or updated as needed.
• All tests are passing (unittest, etc.).

Reviewer Notes

cc @nvmbreughe

[gemini-code-assist]

Note

Gemini is unable to generate a summary for this pull request due to the file types involved not being currently supported.

[nvmbreughe]

LGTM