refactor : add ClearCacheFilesOptions define

Assets/YooAsset/Runtime/FileSystem/Operation/FSClearCacheFilesOperation.cs

@@ -1,6 +1,19 @@
 
 namespace YooAsset
 {
+    internal class ClearCacheFilesOptions
+    {
+        /// <summary>
+        /// 清理模式
+        /// </summary>
+        public string ClearMode;
+
+        /// <summary>
+        /// 附加参数
+        /// </summary>
+        public object ClearParam;
+    }
+
     internal abstract class FSClearCacheFilesOperation : AsyncOperationBase
     {
     }