refact: make resource_utils to use project defined exception and refact code for readability

[darkrush]

make resource_utils to use project defined exception and refact code for readability
Move FileLock in llm_web_kit/model/resource_utils/download_assets.py to FileLockContext in llm_web_kit/model/resource_utils/utils.py

[codecov]

Codecov Report

Attention: Patch coverage is 86.36364% with 15 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
llm_web_kit/model/resource_utils/unzip_ext.py	78.12%	7 Missing ⚠️
...lm_web_kit/model/resource_utils/download_assets.py	76.47%	4 Missing ⚠️
llm_web_kit/config/cfg_reader.py	33.33%	2 Missing ⚠️
llm_web_kit/model/resource_utils/boto3_ext.py	88.88%	1 Missing ⚠️
llm_web_kit/model/resource_utils/utils.py	97.77%	1 Missing ⚠️

@@            Coverage Diff             @@
##              dev     #274      +/-   ##
==========================================
- Coverage   90.68%   89.21%   -1.48%     
==========================================
  Files         116       80      -36     
  Lines        6914     5478    -1436     
==========================================
- Hits         6270     4887    -1383     
+ Misses        644      591      -53     

Files with missing lines	Coverage Δ
...model/resource_utils/singleton_resource_manager.py	100.00% <100.00%> (ø)
llm_web_kit/model/resource_utils/boto3_ext.py	82.00% <88.88%> (-0.98%)	⬇️
llm_web_kit/model/resource_utils/utils.py	97.77% <97.77%> (ø)
llm_web_kit/config/cfg_reader.py	73.33% <33.33%> (+1.90%)	⬆️
...lm_web_kit/model/resource_utils/download_assets.py	95.31% <76.47%> (+3.64%)	⬆️
llm_web_kit/model/resource_utils/unzip_ext.py	84.61% <78.12%> (-11.04%)	⬇️

... and 47 files with indirect coverage changes

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