Include env defaults from variables.properties.env in deep merge

[kevingrismore]

The deep merge for env from the deployment->work pool only worked if the env vars were written directly into the template. This copies down the defaults to include them in the deep merge as well.

Checklist

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[codspeed-hq]

CodSpeed Performance Report

Merging #15692 will not alter performance

_{Comparing fix-worker-env-deep-merge (759cd1b) with main (dcf250b)}

Summary

✅ 3 untouched benchmarks

[kevingrismore]

This one has a weird feel to it, very open to suggestions for other solutions.

[zzstoatzz]

after talking sync, the change makes sense to me

but for the test, can we just parameterize the base job template and have one parameterized test?

[zzstoatzz]

lgtm!