feat: added PURL generation to DartParser

[mastersans]

Related: #3771

References:
pubspec
purl-spec for pub

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 30.00000% with 7 lines in your changes are missing coverage. Please review.

Project coverage is 75.39%. Comparing base (d6cbe40) to head (dc2c413).
Report is 165 commits behind head on main.

Files	Patch %	Lines
cve_bin_tool/parsers/dart.py	30.00%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4004      +/-   ##
==========================================
- Coverage   75.41%   75.39%   -0.02%     
==========================================
  Files         808      820      +12     
  Lines       11983    12600     +617     
  Branches     1598     1711     +113     
==========================================
+ Hits         9037     9500     +463     
- Misses       2593     2744     +151     
- Partials      353      356       +3     

Flag	Coverage Δ
longtests	75.39% <30.00%> (-0.02%)	⬇️

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[joydeep049]

This looks good. I don't think any changes are needed. @mastersans
cc @terriko

[terriko]

Marking this as approved now, but I don't know if I'll merge it before or after release. Since this doesn't affect scan results it really doesn't matter which way we go; I'm just reviewing it now while I'm waiting for some other scans to finish.

[terriko]

Decided to add the links @mastersans had above into the docstring so they're available easily for future reference. Tests are going to re-run now.