Leetcode 2694. Event Emitter

Implement an EventEmitter that maintains ordered listener lists per event name, supporting subscribe (adds a callback and returns an object with an unsubscribe method to remove that listener) and emit (calls all listeners in subscription order with given arguments and returns an array of their results, or an empty array if none). The key challenges are preserving listener order, allowing removal via unsubscribe, and returning the collected callback results.