Fix thread safety issues

[Evangelink]

Summary

Several data structures shared across concurrent test execution threads were not thread-safe, risking corrupted results and lost updates.

Changes

• ParallelRunDataAggregator / DiscoveryDataAggregator: Replace TryGetValue + set pattern with ConcurrentDictionary.AddOrUpdate in metrics aggregation to eliminate lost-update races
• DataCollectionAttachmentManager: Replace List<Task> with ConcurrentBag<Task> for _attachmentTasks; replace ContainsKey + TryAdd TOCTOU pattern with GetOrAdd for both AttachmentSets and _attachmentTasks
• BlameCollector: Replace List<Guid> / Dictionary<Guid, BlameTestObject> with ConcurrentQueue / ConcurrentDictionary; use Interlocked.Increment for _testEndCount; snapshot collections before passing to WriteTestSequence
• TrxLogger / HtmlLogger: Use Interlocked.Increment for all test counters (TotalTestCount, PassedTestCount, FailedTestCount, SkippedTests) to prevent lost updates under concurrent result arrival