refact import transformers and make cache dir alap

[darkrush]

Use function import_transformer to make sure import transformers after set envvar HF_HOME.

def import_transformer():
    os.environ['HF_HOME'] = CACHE_DIR
    os.makedirs(CACHE_DIR, exist_ok=True)
    import transformers

    return transformers

Now, cache dir will not be maked at importing resource_utils but at downloading or unziping.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

@@            Coverage Diff             @@
##              dev     #290      +/-   ##
==========================================
- Coverage   89.92%   89.58%   -0.35%     
==========================================
  Files          85       82       -3     
  Lines        5630     5548      -82     
==========================================
- Hits         5063     4970      -93     
- Misses        567      578      +11     

Files with missing lines	Coverage Δ
llm_web_kit/model/html_classify/model.py	100.00% <100.00%> (ø)
llm_web_kit/model/policical.py	54.43% <100.00%> (-0.57%)	⬇️
llm_web_kit/model/porn_detector.py	74.11% <100.00%> (ø)
...lm_web_kit/model/resource_utils/download_assets.py	95.83% <100.00%> (+0.04%)	⬆️
llm_web_kit/model/resource_utils/unzip_ext.py	95.83% <100.00%> (+0.08%)	⬆️
llm_web_kit/model/resource_utils/utils.py	96.55% <100.00%> (+0.12%)	⬆️

... and 13 files with indirect coverage changes

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