feat: merge extractor and detector flags into plugins

[G-Rath]

This removes the external distinction between extractors and detectors in favor of just plugins, which matches how they're represented in scalibr

[codecov-commenter]

Codecov Report

❌ Patch coverage is 98.01980% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 67.50%. Comparing base (c7499c2) to head (677cb71).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/osvscanner/scan.go	91.30%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2146      +/-   ##
==========================================
- Coverage   67.58%   67.50%   -0.08%     
==========================================
  Files         171      170       -1     
  Lines       16271    16232      -39     
==========================================
- Hits        10996    10957      -39     
  Misses       4600     4600              
  Partials      675      675              

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[another-rex]

LGTM as well, though need to resolve the conflicts before the diffs are correct.