Add Documentation for Missing Fields in Challenge and Challenge Phase Models and configuration.md (Excluding Code Upload Fields)

**Description:**

Some fields used in the Challenge model are missing from the public documentation, particularly the [`[configuration.md](https://github.com/Cloud-CV/EvalAI/blob/master/docs/configuration.md)`](https://github.com/Cloud-CV/EvalAI/blob/master/docs/configuration.md) file. These undocumented fields make it difficult for challenge hosts to fully understand and utilize the configuration options available.

📄 **Areas to Update:**

1. **Challenge Configuration Guide:**

* 📂 File: `configuration.md`
* 🛠️ Action: Add detailed explanations, allowed values, and example usage for all relevant fields used in challenge configuration.

2. **Challenge Model Documentation:**

* Ensure all documented fields are up to date with the current `Challenge`, `ChallengePhase`, `Leaderboard`, and `DatasetSplit` models.

🚫 **Important Note:**
Do **not** include any fields that were previously used for **code upload** or **static code upload** challenges, as those features are no longer supported.

📌 **Examples of Missing or Under-Documented Fields (non-code-upload related):**

* `remote_evaluation`
* `submission_public`
* Others present in the current model definitions

Improving this documentation will streamline challenge onboarding, reduce confusion, and ensure consistency across hosted challenges.