Cannot run vectordb-bench in offline env

Meet some issues when run vectordb-bench in offline env.

Reproduce steps:

1. download cohere_medium_1m dataset
2. run milvus standalone
3. install vectordb-bench official pip package

pip install vectordb-bench
pip install vectordb-bench milvus

4. run "init_bench", and then run task, flow will error out with this traceback:

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/caiyd/miniconda3/envs/vdb/lib/python3.11/site-packages/vectordb_bench/interface.py", line 182, in _async_task_v2
    case_res.metrics = runner.run(drop_old)
                       ^^^^^^^^^^^^^^^^^^^^
  File "/home/caiyd/miniconda3/envs/vdb/lib/python3.11/site-packages/vectordb_bench/backend/task_runner.py", line 120, in run
    self._pre_run(drop_old)
  File "/home/caiyd/miniconda3/envs/vdb/lib/python3.11/site-packages/vectordb_bench/backend/task_runner.py", line 112, in _pre_run
    self.ca.dataset.prepare(self.dataset_source, filters=self.ca.filters)
  File "/home/caiyd/miniconda3/envs/vdb/lib/python3.11/site-packages/vectordb_bench/backend/dataset.py", line 368, in prepare
    source.reader().read(
  File "/home/caiyd/miniconda3/envs/vdb/lib/python3.11/site-packages/vectordb_bench/backend/data_source.py", line 133, in read
    if (not local_file.exists()) or (not self.validate_file(remote_file, local_file)):
                                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/caiyd/miniconda3/envs/vdb/lib/python3.11/site-packages/vectordb_bench/backend/data_source.py", line 149, in validate_file
    info = self.fs.info(remote)
           ^^^^^^^^^^^^^^^^^^^^
  File "/home/caiyd/miniconda3/envs/vdb/lib/python3.11/site-packages/fsspec/asyn.py", line 118, in wrapper
    return sync(self.loop, func, *args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

5. want to comment out this line "if (not local_file.exists()) or (not self.validate_file(remote_file, local_file)):",
   so I uninstall vectordb-bench, and install it locally, but it cannot start up

(vdb)  ~/work/zilliz/VectorDBBench/ [tags/v1.0.10] pip uninstall -y vectordb-bench               
Found existing installation: vectordb-bench 1.0.11
Uninstalling vectordb-bench-1.0.11:
  Successfully uninstalled vectordb-bench-1.0.11
(vdb)  ~/work/zilliz/VectorDBBench/ [tags/v1.0.10] 
(vdb)  ~/work/zilliz/VectorDBBench/ [tags/v1.0.10] pip cache purge                
Files removed: 286 (16.3 MB)
(vdb)  ~/work/zilliz/VectorDBBench/ [tags/v1.0.10] 
(vdb)  ~/work/zilliz/VectorDBBench/ [tags/v1.0.10] pip install -e ".[milvus]"
Obtaining file:///home/caiyd/work/zilliz/VectorDBBench
  Installing build dependencies ... done
......
55130281d18c9ffcdf77cae9
  Stored in directory: /tmp/pip-ephem-wheel-cache-n7c1wn_2/wheels/ac/03/a2/762233e655726a69db9d9b05989bd48a40b5ae020618dc4590
Successfully built vectordb-bench
Installing collected packages: vectordb-bench
Successfully installed vectordb-bench-1.0.10
(vdb)  ~/work/zilliz/VectorDBBench/ [tags/v1.0.10] 
(vdb)  ~/work/zilliz/VectorDBBench/ [tags/v1.0.10] pip list | grep vectordb-bench
130:vectordb-bench              1.0.10      /home/caiyd/work/zilliz/VectorDBBench
(vdb)  ~/work/zilliz/VectorDBBench/ [tags/v1.0.10] 
(vdb)  ~/work/zilliz/VectorDBBench/ [tags/v1.0.10] init_bench
Traceback (most recent call last):
  File "/home/caiyd/miniconda3/envs/vdb/bin/init_bench", line 3, in <module>
    from vectordb_bench.__main__ import main
  File "/home/caiyd/work/zilliz/VectorDBBench/vectordb_bench/__main__.py", line 6, in <module>
    from . import config
ImportError: cannot import name 'config' from 'vectordb_bench' (unknown location)
(vdb)  ~/work/zilliz/VectorDBBench/ [tags/v1.0.10] 

Start with vectordb_bench/backend/data_source.py, especially read() and validate_file(), and reproduce the offline dataset flow through init_bench. Also inspect vectordb_bench/main.py and the package's config import for the editable-install failure. Done should mean the benchmark can use the downloaded dataset offline and init_bench starts from a local installation.