feat(cloudformation-diff): add Fn::ForEach intrinsic function diff support

[awsmadi]

• Add ForEachDiffFormatter class for specialized ForEach formatting
• Integrate ForEach detection and formatting into main diff logic
• Export ForEach utilities from package index
• Add comprehensive test coverage for ForEach diff scenarios

Fixes #

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.70%. Comparing base (e553d85) to head (8a3de34).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1063   +/-   ##
=======================================
  Coverage   87.70%   87.70%           
=======================================
  Files          72       72           
  Lines       10121    10121           
  Branches     1336     1336           
=======================================
  Hits         8877     8877           
  Misses       1219     1219           
  Partials       25       25           

Flag	Coverage Δ
suite.unit	87.70% <ø> (ø)

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