chore(celery): Allow setting 2 more options through environmental variables

[ZeleniJure]

Problem

More options added when running celery in order to tweak things easier.

Changes

Celery options as environmental variables.

👉 Stay up-to-date with PostHog coding conventions for a smoother review.

Does this work well for both Cloud and self-hosted?

Yes

How did you test this code?

Running the script manually

[github-actions[bot]]

Size Change: 0 B

Total Size: 1.06 MB

ℹ️ View Unchanged

| Filename | Size | | :--- | :---: | | `frontend/dist/toolbar.js` | 1.06 MB |

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[ZeleniJure]

we don't have these command line parameters