Prune stale HTTPRoutes when tags are removed from Ingress rules

[kahirokunn]

• Add pruning in reconcileIngress to delete owned HTTPRoutes not referenced
• Add unit test to verify stale route deletion behavior

/kind bug

Fixes #895

Release Note:

Fix a bug where HTTPRoutes could remain after tags were removed. Stale routes are now deleted during reconciliation.

[knative-prow]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all

[knative-prow]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: kahirokunn
Once this PR has been reviewed and has the lgtm label, please assign dprotaso for approval. For more information see the Code Review Process.

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[codecov]

Codecov Report

❌ Patch coverage is 81.81818% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.50%. Comparing base (b658b58) to head (31521b5).

Files with missing lines	Patch %	Lines
pkg/reconciler/ingress/ingress.go	81.81%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #894      +/-   ##
==========================================
+ Coverage   76.45%   76.50%   +0.04%     
==========================================
  Files          17       17              
  Lines        1253     1264      +11     
==========================================
+ Hits          958      967       +9     
- Misses        261      262       +1     
- Partials       34       35       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[kahirokunn]

@dprotaso Hello! I'd be grateful if you could leave a review when you have a moment! 🙏