feat: add flag to skip env var fetching

[davbree]

🎉 Thanks for submitting a pull request! 🎉

Summary

Introduce internal option --offline-env to disable using any env vars fetched from the API.
This offers better support for the case of receiving all env vars externally (via devbot).

ref CRE-1078

---

For us to review and ship your PR efficiently, please perform the following steps:

• Open a bug/issue before writing your code 🧑‍💻. This ensures we can discuss the changes and get feedback from everyone that should be involved. If you`re fixing a typo or something that`s on fire 🔥 (e.g. incident related), you can skip this step.
• Read the contribution guidelines 📖. This ensures your code follows our style guide and
  passes our tests.
• Update or add tests (if any source code was changed or added) 🧪
• Update or add documentation (if features were changed or added) 📝
• Make sure the status checks below are successful ✅

A picture of a cute animal (not mandatory, but encouraged)

[github-actions]

📊 Benchmark results

Comparing with a265859

• Dependency count: 1,212 (no change)
• Package size: 313 MB (no change)
• Number of ts-expect-error directives: 976 (no change)

[lukasholzer]

why cannot we use the existing --offline flag for it?

[davbree]

We still want to fetch the site config (for the dev command and target port). I could provide that from bitballoon as well in the future (CRE-1431) and then we can use --offline (and remove --offline-env)

[lukasholzer]

We still want to fetch the site config (for the dev command and target port). I could provide that from bitballoon as well in the future (CRE-1431) and then we can use --offline (and remove --offline-env)

As this is public API on the CLI we should provide that probably first to be able to leverage the --offline flag.

[mraerino]

i think there is value in having a flag just for "don't fetch env vars". using --offline means that no interaction can happen, but we might want the CLI to talk to services regardless of if it is supposed to fetch env vars

[davbree]

I'm using hideHelp(true) to keep things internal (like we do for other parameters). Makes it easier to do this not all together..