Refactor ELO rating update logic in GhostTrainer

[OMS1996]

• Extract ELO rating update logic from _process_trajectory into a new method update_elo_ratings
• Improves code organization and reusability
• No functional changes to the ELO update algorithm

Proposed change(s)

• Created a new method update_elo_ratings in the GhostTrainer class
• Modified the _process_trajectory method to call update_elo_ratings
• The new method encapsulates the logic for updating ELO ratings based on trajectory outcomes

This is a very simple change for readability that is all.

Useful links (Github issues, JIRA tickets, ML-Agents forum threads etc.)

N/A

Types of change(s)

• Bug fix
• New feature
• Code refactor
• Breaking change
• Documentation update
• Other (please describe)

Checklist

• Added tests that prove my fix is effective or that my feature works
• Updated the changelog (if applicable)
• Updated the documentation (if applicable)
• Updated the migration guide (if applicable)

Other comments

This refactor improves the modularity of the ELO rating update logic, making it easier to maintain and potentially reuse in other parts of the codebase if needed. The functionality remains unchanged, so existing behavior should not be affected. However, it's recommended to run the existing test suite to ensure no unintended side effects.

[CLAassistant]

All committers have signed the CLA.

[OMS1996]

@miguelalonsojr @erikfrey @furkan-celik I was wondering if you could review this, Just want to get my feet wet in this repo.