Fix env var deep merge order on worker

[kevingrismore]

Changes merge order so overlapping keys select deployment env vars over work pool env vars.

Checklist

• This pull request references any related issue by including "closes <link to issue>"
  • If no issue exists and your change is not a small fix, please create an issue first.
• If this pull request adds new functionality, it includes unit tests that cover the changes
• If this pull request removes docs files, it includes redirect settings in mint.json.
• If this pull request adds functions or classes, it includes helpful docstrings.

[codspeed-hq]

CodSpeed Performance Report

Merging #16045 will not alter performance

_{Comparing fix-env-deep-merge-order (15f1e66) with main (c2a3fb5)}

Summary

✅ 3 untouched benchmarks

[zzstoatzz]

thank you! just a couple requests

[zzstoatzz]

lgtm!