Refactor ep upload to use Fireworks SDK + Auto-generate flags (#379)

* remove auth ini logic

* update fireworks-ai and make it a core dependency

* wrong package

* use FireworkS SDK for Secret automation

* uv lock

* update

* use latest SDK

* update

* update

* update

* Refactor _load_secrets_from_env_file to return all environment variables and remove API_KEY filtering logic

* remove legacy reward kit evaluator upload code

* delete more legacy code

* fix test

* Add secret selection prompt for Fireworks upload in CLI

- Introduced `_prompt_select_secrets` function to allow users to select environment variables for upload as secrets.
- Implemented fallback selection method for non-interactive environments.
- Updated `upload_command` to utilize the new secret selection logic.
- Enhanced user experience with improved prompts and error handling.
- Added `_get_questionary_style` function for consistent CLI styling.

* try again

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Co-authored-by: Derek Xu <[email protected]>

Author: dphuang2