[worker] warn on unknown build environment

[gwdp]

Why

A workflow job with an environment that doesn't exist (e.g. staging, vs development/preview/production) gets no warning. It silently resolves to zero environment variables and fails later in a confusing, unrelated-looking way (e.g. the app config failing to read).

How

Warn in the "Spin up build environment" phase when the job's environment isn't development/preview/production.

Test Plan

Ran this job against a local worker:

jobs:
  verify_fingerprint_job_outputs:
    name: Verify fingerprint job outputs
    type: custom
    environment: staging
    runs_on: linux-medium
    steps:
      - run: echo "=== test job ==="

[gwdp]

• [worker] warn on unknown build environment #3952 👈 (View in Graphite)
• main

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 59.27%. Comparing base (9247f3c) to head (bf57252).
⚠️ Report is 8 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3952      +/-   ##
==========================================
+ Coverage   59.18%   59.27%   +0.10%     
==========================================
  Files         935      936       +1     
  Lines       41075    41159      +84     
  Branches     8648     8675      +27     
==========================================
+ Hits        24306    24393      +87     
+ Misses      16674    16666       -8     
- Partials       95      100       +5     

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[gwdp]

started with a new build phase but thought it was overkill and moved here. Let me know if you have any different thoughts

[github-actions]

⏩ The changelog entry check has been skipped since the "no changelog" label is present.

[sjchmiela]

We support custom environments, so specifying a not-known environment is not an issue per se as long as the user has environment variables in that environment?

Initially I thought we might color the environment pill yellow on workflow run page if the environment has no variables, but that would color it yellow if a user does not use EAS Environment Variables at all which is bad?

Maybe we do this ^ but only if environment is not one of the known environments? Or sth like that