[Bug] Memory Leak and Stats Pollution via unmanaged ThreadLocal in ThreadLocalStatisticsCollector

Describe the bug
There is a potential Unintentional ThreadLocal Leak (UTL) in ThreadLocalStatisticsCollector. The class relies on consumers manually calling resetThread() at "request boundaries" to clear the ThreadLocal<SimpleStatisticsCollector>.

However, in typical GraphQL environments (reactive streams, async gateways, or standard thread pools), threads are heavily reused. If an unhandled exception occurs or a developer forgets to call resetThread(), the SimpleStatisticsCollector object is permanently retained by the worker thread.

Impact:

1. Data Pollution: Subsequent requests processed by the dirty thread will inherit the accumulated statistics of previous requests, leading to completely distorted metrics.
2. Memory Leak (Type I UTL): As more threads in the pool retain these un-cleared statistics objects over time, the heap usage will grow linearly, potentially leading to an OutOfMemoryError in high-throughput applications.

To Reproduce
Here is a simplified code example demonstrating the data pollution in a thread-pool environment when resetThread() is missed (e.g., bypassed due to an exception):

import org.dataloader.stats.ThreadLocalStatisticsCollector;
import java.util.concurrent.*;

public class UTLReproduction {
    public static void main(String[] args) throws Exception {
        ThreadLocalStatisticsCollector collector = new ThreadLocalStatisticsCollector();
        // Simulate a web server with a reusable thread pool
        ExecutorService threadPool = Executors.newFixedThreadPool(1);

        // Request 1: Execution completes but resetThread() is missed (e.g. exception thrown)
        threadPool.submit(() -> {
            collector.incrementLoadCount();
            // Developer forgets to put collector.resetThread() in a finally block
        }).get();

        // Request 2: A new incoming request reuses the same dirty thread
        threadPool.submit(() -> {
            long loadCount = collector.getStatistics().getLoadCount();
            // BUG: loadCount is 1 instead of 0! The new request is polluted by Request 1.
            System.out.println("New Request Load Count (Expected 0): " + loadCount);
        }).get();
        
        threadPool.shutdown();
    }
}

まず ThreadLocalStatisticsCollector を読み、特に ThreadLocal の使用、getStatistics()、resetThread() を確認します。resetThread() をスキップした場合にリクエスト間で統計情報が保持されるかを検証するため、提供された fixed-thread-pool の再現コードを実行します。Done には、リクエスト間の汚染と保持を防ぐための方針を決定した方法と、再現したシナリオをカバーするテストを含める必要があります。