fix deprecated GitHub Actions

[nodivbyzero]

Summary

• Replace unmaintained actions-rs/toolchain@v1 with dtolnay/rust-toolchain@stable to fix Node.js 20 deprecation warning
• Use gotestsum's built-in --format github-actions instead of separate guyarb/golang-test-annotations action to fix set-output deprecation

[posit-snyk-bot]

✅ Snyk checks have passed. No issues have been found so far.

Status	Scan Engine	Critical	High	Medium	Low	Total (0)
✅	Open Source Security	0	0	0	0	0 issues
✅	Licenses	0	0	0	0	0 issues

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