Ignore stage names in dockerfile verify

[slmsbrhgn]

Summary

Fixes #3880, allowing dockerfile verify to validate Dockerfiles where stage names are used in FROM statements

Release Note

• Fixed bug that made dockerfile verify fail when a stage name was used in FROM statement

Documentation

N/A

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 36.72%. Comparing base (2ef6022) to head (6d3a32d).
Report is 215 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3881      +/-   ##
==========================================
- Coverage   40.10%   36.72%   -3.38%     
==========================================
  Files         155      203      +48     
  Lines       10044    12786    +2742     
==========================================
+ Hits         4028     4696     +668     
- Misses       5530     7507    +1977     
- Partials      486      583      +97     

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