refactor: remove redundant internal packages migrated to osv-scalibr

[cuixq]

#2675

This PR cleans up the codebase by removing internal implementations that have been migrated to osv-scalibr.

• Deleted the following packages and their associated testdata:
  • internal/datasource
  • internal/resolution
  • internal/remediation
  • internal/tui
  • internal/utility/maven
• Moved func NewInsightsAlphaClient from internal/datasource to internal/depsdev.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 7.69231% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 79.72%. Comparing base (f6c921c) to head (ab4bb65).

Files with missing lines	Patch %	Lines
internal/depsdev/depsdev.go	0.00%	12 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2720      +/-   ##
==========================================
+ Coverage   71.44%   79.72%   +8.28%     
==========================================
  Files         164      117      -47     
  Lines       12075     8016    -4059     
==========================================
- Hits         8627     6391    -2236     
+ Misses       2829     1248    -1581     
+ Partials      619      377     -242     

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[michaelkedar]

I love deleting code 🙂