[FIX Download] update converted logic & fix hf hub download subfolder bug

[JunnYu]

PR types

PR changes

Description

1. hf hub 下载的时候不需要 给filename拼subfolder，否则会出现 subfolder/subfolder/filename
2. 权重转换的时候自动检测同级目录是否存在 model_state.pdparams文件，如果存在就直接使用并load_file成为state_dict
3. 加载转换后的paddle权重文件的逻辑进行修改，先是通过检测与torch同级目录的paddle文件是否存在

   PaddleNLP/paddlenlp/transformers/model_utils.py

   Line 2141 in bb6c735

   if not os.path.exists(converted_paddle_weights):

   ，如果存在就直接加载（原先的时候第二次加载是不会走这里的逻辑，现在统一一下，走这里）

[codecov]

Codecov Report

Attention: 8 lines in your changes are missing coverage. Please review.

Comparison is base (fff730e) 57.28% compared to head (bb6c735) 57.27%.

Files	Patch %	Lines
paddlenlp/transformers/model_utils.py	42.85%	8 Missing ⚠️

Additional details and impacted files

@@               Coverage Diff               @@
##           release/2.7    #7911      +/-   ##
===============================================
- Coverage        57.28%   57.27%   -0.01%     
===============================================
  Files              584      584              
  Lines            87747    87747              
===============================================
- Hits             50262    50257       -5     
- Misses           37485    37490       +5     

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