feat: Add async flush method

src/Uno.DevTools.Telemetry/Telemetry.cs

@@ -123,6 +123,20 @@ public void Flush()
             }
         }
 
+        public async Task FlushAsync()
+        {
+            if (!Enabled || _trackEventTask == null)
+            {
+                return;
+            }
+
+            // Skip the wait if the task has not yet been activated
+            if (_trackEventTask.Status != TaskStatus.WaitingForActivation)
+            {
+                await _trackEventTask;
+            }
+        }
+
         public void Dispose()
         {
             _persistenceChannel?.Dispose();