fix(scripts): await release asset downloads

[wangjingshuiku]

The release-draft helper starts each asset pipeline inside forEach(async ...), so download() resolves before the pipelines finish and download failures are detached from its promise.

This change awaits Promise.all(assetList.map(...)) and handles the returned top-level promise by reporting the error and setting a non-zero exit code. The script now completes only after every asset has been written.

Validation: node --check scripts/download-binaries-from-release-draft.js.

[wangjingshuiku]

Hi @chenyukang, when you have a moment, could you take a look at this PR? Thanks!

It fixes a small issue where the release asset download helper could return before its async download tasks had completed, and download failures could escape the top-level promise.

[chenyukang]

Thanks!