Implement Position-Based Random Magic Item Distribution

[SergeantSerk]

This PR introduces a system for distributing random magic items to racers, where the selection probability is weighted by their current effective position on the scoreboard. This ensures that the random magic item are dynamically tuned to a player's performance during the race.

Key Changes:

• MagicSystem Integration: Introduced a new MagicSystem to encapsulate logic for managing magic items and logic within a race
• Position-Based Weighting: Implemented logic to calculate an effective racer position, which is then used to determine the probability weights for specific magic item types. This allows for "catch-up" mechanics or performance-scaled rewards
• Configurable Weights: Magic item weights are now stored and managed via configuration (magic.yaml), allowing designers to easily tweak how position affects distribution without code changes
• Race Tracker Integration: Updated RaceTracker and the race update loop to trigger magic item requests and handle state transitions (e.g. when a racer's magic gauge is ready)