Enabled *.mlpackage models usage. (#814)

* updated archive_cached_helper to make possible handle mlpackage zip archive.

* updated lu script to convert mobileBert to the coreml

* updated archive_cache_helper to support mlpackage loading(*.mlpackage.zip)

* code cleanup for archive_cache_helper

* reverted lu.py script

* archive helper code clean

flutter/lib/resources/archive_cache_helper.dart

@@ -41,14 +41,22 @@ class ArchiveCacheHelper {
       final archive =
           ZipDecoder().decodeBytes(await File(archivePath).readAsBytes());
 
-      for (final archiveFile in archive) {
-        final filePath = '${result.path}/${archiveFile.name}';
-        final file = await File(filePath).create(recursive: true);
-
-        final data = archiveFile.content as List<int>;
-        await file.writeAsBytes(data);
+      var archiveParentPath = result.path;
+      if (!archive.first.isFile) {
+        archiveParentPath = result.parent.path;
       }
 
+      for (int i = 0; i < archive.files.length; i++) {
+        final archiveFile = archive.files[i];
+        final itemPath = '$archiveParentPath/${archiveFile.name}';
+        if (archiveFile.isFile) {
+          final file = await File(itemPath).create(recursive: true);
+          final data = archiveFile.content as List<int>;
+          await file.writeAsBytes(data);
+        } else if (i != 0) {
+          await Directory(itemPath).create(recursive: true);
+        }
+      }
       return result;
     } catch (e) {
       await result.delete(recursive: true);