YAML safe load and assert removing

[babenek]

Description

Please include a summary of the change and which is fixed.

• Use YAML safe load
• Removed asserts in code
• Fix PNG iTXt field extraction

How has this been tested?

Please describe the tests that you ran to verify your changes.

• UnitTest
• Benchmark

[codecov-commenter]

Codecov Report

❌ Patch coverage is 68.42105% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.29%. Comparing base (b84e754) to head (ab00854).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
credsweeper/scanner/scan_type/multi_pattern.py	0.00%	1 Missing and 1 partial ⚠️
credsweeper/scanner/scan_type/pem_key_pattern.py	0.00%	1 Missing and 1 partial ⚠️
credsweeper/scanner/scan_type/single_pattern.py	33.33%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #808      +/-   ##
==========================================
- Coverage   92.31%   92.29%   -0.03%     
==========================================
  Files         144      145       +1     
  Lines        5833     5890      +57     
  Branches      946      960      +14     
==========================================
+ Hits         5385     5436      +51     
- Misses        289      293       +4     
- Partials      159      161       +2     

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