🌱 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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