Support unknown item types for scheme ls

[rekby]

Add unknown entry type for scheme enum and return it instead of panic on unknown item type

stacktrace:

Traceback (most recent call last):
  File "/Users/rekby/projects/rekby/tmp-py/main.py", line 43, in <module>
    main()
  File "/Users/rekby/projects/rekby/tmp-py/main.py", line 38, in main
    print(conn.scheme_client.list_directory("/pre-prod_ydb_public/aoe2jtpkkegdfvl3ltb6/cc89m3nkdqhk02shilub"))
  File "/Users/rekby/projects/rekby/tmp-py/venv/lib/python3.10/site-packages/ydb/scheme.py", line 407, in list_directory
    return self._driver(
  File "/Users/rekby/projects/rekby/tmp-py/venv/lib/python3.10/site-packages/ydb/tracing.py", line 74, in wrapper
    return f(self, *args, **kwargs)
  File "/Users/rekby/projects/rekby/tmp-py/venv/lib/python3.10/site-packages/ydb/pool.py", line 465, in __call__
    res = connection(
  File "/Users/rekby/projects/rekby/tmp-py/venv/lib/python3.10/site-packages/ydb/connection.py", line 490, in __call__
    else wrap_result(rpc_state, response, *wrap_args)
  File "/Users/rekby/projects/rekby/tmp-py/venv/lib/python3.10/site-packages/ydb/scheme.py", line 326, in _wrap_list_directory_response
    children.append(_wrap_scheme_entry(children_item))
  File "/Users/rekby/projects/rekby/tmp-py/venv/lib/python3.10/site-packages/ydb/scheme.py", line 302, in _wrap_scheme_entry
    getattr(SchemeEntryType, _apis.ydb_scheme.Entry.Type.Name(entry_pb.type)),
  File "/Users/rekby/projects/rekby/tmp-py/venv/lib/python3.10/site-packages/google/protobuf/internal/enum_type_wrapper.py", line 73, in Name
    raise ValueError('Enum {} has no name defined for value {!r}'.format(
ValueError: Enum Type has no name defined for value 17