Tune speedtest parallelism

Set `MaxDegreeOfParallelism` explicitly to the current selection size in three speed test parallel sections so task fan-out matches the workload. Also wrapped socket connect timing in a catch block that ignores connection exceptions, preventing a failed connect from aborting the flow while still completing cleanup.
https://github.com/2dust/v2rayN/issues/10246

v2rayN/ServiceLib/Services/SpeedtestService.cs

@@ -210,6 +210,7 @@ public class SpeedtestService(Config config, Func<SpeedTestResult, Task> updateF
 
             var parallelOptions = new ParallelOptions
             {
+                MaxDegreeOfParallelism = lst.Count,
                 CancellationToken = ct,
             };
 
@@ -291,6 +292,7 @@ public class SpeedtestService(Config config, Func<SpeedTestResult, Task> updateF
 
             var parallelOptions = new ParallelOptions
             {
+                MaxDegreeOfParallelism = selecteds.Count,
                 CancellationToken = ct,
             };
 
@@ -381,6 +383,7 @@ public class SpeedtestService(Config config, Func<SpeedTestResult, Task> updateF
 
             var parallelOptions = new ParallelOptions
             {
+                MaxDegreeOfParallelism = selecteds.Count,
                 CancellationToken = ct,
             };
 
@@ -570,6 +573,10 @@ public class SpeedtestService(Config config, Func<SpeedTestResult, Task> updateF
             await clientSocket.ConnectAsync(endPoint, linkedCts.Token).ConfigureAwait(false);
             responseTime = (int)timer.ElapsedMilliseconds;
         }
+        catch
+        {
+            // Ignore
+        }
         finally
         {
             timer.Stop();