改进模拟数据生成器，代码质量优化

MesETL.App/Services/ETL/MySqlDestination.cs

@@ -64,7 +64,7 @@ public partial class MySqlDestination : IDisposable, IAsyncDisposable
         if (_recordCache.Count == 0)
             return;
 
-        var cmd = _conn.CreateCommand();
+        await using var cmd = _conn.CreateCommand();
         cmd.CommandTimeout = 0;
        
         try
@@ -255,11 +255,13 @@ public partial class MySqlDestination : IDisposable, IAsyncDisposable
     {
         _conn.Close();
         _conn.Dispose();
+        _recordCache.Clear();
     }
 
     public async ValueTask DisposeAsync()
     {
         await _conn.CloseAsync();
         await _conn.DisposeAsync();
+        _recordCache.Clear();
     }
 }