⚠️ Remove dependencydiff files and related tests

[naveensrinivasan]

• Remove depedencydiff as we are building something similar to this Add Dependency Analysis Action and Dockerfile scorecard-action#1095

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• Tests for the changes have been added (for bug fixes/features)

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The dependencydiff package has been removed. 

[codecov]

Codecov Report

Merging #3053 (2c0ddfe) into main (0888bad) will decrease coverage by 5.33%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3053      +/-   ##
==========================================
- Coverage   62.91%   57.59%   -5.33%     
==========================================
  Files         166      136      -30     
  Lines       12461    11072    -1389     
==========================================
- Hits         7840     6377    -1463     
- Misses       4178     4302     +124     
+ Partials      443      393      -50     

[github-actions]

Stale pull request message

[spencerschrock]

Given it's a breaking change, do we want to add it to the v5 tracker so we can do it at major bump? (I don't see anything dependents https://pkg.go.dev/github.com/ossf/scorecard/v4@v4.10.5/dependencydiff, but we can't know for sure)

In the short term we could mark as deprecated?

[naveensrinivasan]

#3125