feat(llc): Add insertAt to upsert for controlling insertion position

[xsahil03x]

This pull request adds a new feature to the upsert method in the ListExtensions utility, allowing callers to specify exactly where a new element should be inserted in the list using an insertAt parameter. This provides more flexibility for list updates and is thoroughly tested with various scenarios to ensure correct behavior.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 28.61%. Comparing base (296d4b8) to head (3d3d40d).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #21      +/-   ##
==========================================
+ Coverage   28.39%   28.61%   +0.22%     
==========================================
  Files          49       49              
  Lines         972      975       +3     
==========================================
+ Hits          276      279       +3     
  Misses        696      696              

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