Refine G407 to improve detection and coverage of hardcoded nonces

[oittaa]

Improves the current situation. Related to #1211

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 88.18381% with 54 lines in your changes missing coverage. Please review.
✅ Project coverage is 65.22%. Comparing base (1216c9b) to head (3b57098).
⚠️ Report is 157 commits behind head on master.

Files with missing lines	Patch %	Lines
analyzers/hardcoded_nonce.go	88.70%	16 Missing and 11 partials ⚠️
analyzers/slice_bounds.go	77.50%	10 Missing and 8 partials ⚠️
analyzers/util.go	93.33%	4 Missing and 2 partials ⚠️
analyzers/conversion_overflow.go	93.33%	1 Missing and 2 partials ⚠️
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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1460      +/-   ##
==========================================
- Coverage   68.49%   65.22%   -3.28%     
==========================================
  Files          75       79       +4     
  Lines        4384     5064     +680     
==========================================
+ Hits         3003     3303     +300     
- Misses       1233     1589     +356     
- Partials      148      172      +24     

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[oittaa]

You can drop the benchmark file if you want to, but I included it in case you want to test with it. It's not very real worldy but I just needed something to compare with. Below are the results I got from it and obviously analyzing small applications won't get anything close to these speedups.

Performance Comparison:

Analyzer	Current Master	This Build	Speedup	Complexity Scenario
G602 (Slice Bounds)	969.46 ms	22.97 ms	~42x	500 levels of serial re-slicing (recursive depth).
G115 (Overflow)	93.14 ms	29.28 ms	~3x	300 nested if statements + 1,000 conversions.
G407 (Nonce)	0.022 ms	0.016 ms	~1.4x	1,000-level assignment chain for hardcoded IV.