Update `DEFAULT_RUNNER_LABELS` array to match currently supported runners

[kfess]

Is your feature request related to a problem? Please describe.

The DEFAULT_RUNNER_LABELS array in GitHub Actions language services contains outdated runner labels, causing VSCode to suggest deprecated runners while missing current ones in auto-completion.
I've validated a lot of available runners and confirmed the current implementation doesn't match GitHub's supported environments.

Describe the solution you'd like

Update the DEFAULT_RUNNER_LABELS array to remove unsupported runners (ubuntu-18.04, ubuntu-20.04, macos-10.15, macos-11, macos-12) and add current ones (ubuntu-24.04, windows-2025, macos-13/14/15, ARM runners, etc.) based on my research.

• GitHub Actions Results
• Summary

Additional context

I verified that VSCode's auto-completion directly uses this array.
I noticed this issue while studying the codebase to better understand the "Context access might be invalid" problem. The extension is very very helpful - this update would make it even better.

Reference

• https://docs.github.com/ja/actions/using-github-hosted-runners/using-github-hosted-runners/about-github-hosted-runners
• https://github.com/actions/runner-images

I'd be happy to contribute a PR to fix this issue if you think it would be helpful.
Let me know if I should proceed with implementing this update or if you'd prefer a different approach.

[ericsciple]

• Update default runner image labels #325