🌱 Refactor NewBundleFS test utility to builder pattern

[perdasilva]

Description

While doing some refactoring work to fix a bug, it became clear I'd need better test tooling to create test bundle filesystems. This PR updates the NewBundleFS utility using the builder pattern to help compose a valid registry+v1 bundle FS for testing

Reviewer Checklist

• API Go Documentation
• Tests: Unit Tests (and E2E Tests, if appropriate)
• Comprehensive Commit Messages
• Links to related GitHub Issue(s)

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[codecov]

Codecov Report

❌ Patch coverage is 90.62500% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 72.61%. Comparing base (55d9dfb) to head (1ccac24).
⚠️ Report is 7 commits behind head on main.

Files with missing lines	Patch %	Lines
...ontroller/rukpak/util/testing/bundlefs/bundlefs.go	90.47%	3 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2237      +/-   ##
==========================================
+ Coverage   71.87%   72.61%   +0.73%     
==========================================
  Files          86       86              
  Lines        8474     8592     +118     
==========================================
+ Hits         6091     6239     +148     
+ Misses       1982     1943      -39     
- Partials      401      410       +9     

Flag	Coverage Δ
e2e	38.58% <0.00%> (-0.53%)	⬇️
experimental-e2e	45.73% <0.00%> (-0.49%)	⬇️
unit	57.77% <90.62%> (+0.84%)	⬆️

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[pedjak]

/lgtm

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: pedjak, thetechnick

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